Preliminary Requirements

Safety Requirements

WARNING

IT IS THE RESPONSIBILITY OF THE OPERATOR TO OBTAIN AND OBSERVE THE MANUFACTURER'S MATERIAL SAFETY SHEETS FOR MATERIAL SAFETY INFORMATION (SUCH AS HAZARDOUS INGREDIENTS; PHYSICAL/CHEMICAL CHARACTERISTICS; FIRE, EXPLOSION, REACTIVITY, AND HEALTH HAZARD DATA; PRECAUTIONS FOR SAFE HANDLING; AND USE AND CONTROL MEASURES), AND ALSO TO TAKE LOCAL REGULATIONS INTO CONSIDERATION.

Procedure

1. SUBTASK 70-34-03-860-102 Quality Control Procedure

   1. Development of Operator Capability.

      1. IAE recommends that the customer includes the subsequent qualification procedures for equipment, operators, coatings, and powders:

         1. Initial Qualification to Step.

         2. Re-qualification to Step.

         3. Periodic or Routine Qualification Testing to Step.

   2. Data Records.

      1. Record all parameters on a process operation sheet so that parameters can be related to coating defects. Refer to general data and the example of a plasma coating schedule form illustrated in SPM TASK 70-34-03-340-501.

   3. Nozzle Life.

      1. Of special interest is the rate of deterioration of the nozzle. The number of parts which can be grouped together and sprayed between sets of test panels is controlled by this rate of deterioration. This deterioration rate will help to identify a nozzle life that will deliver consistent, satisfactory performance.

2. SUBTASK 70-34-03-860-103 Initial Qualification

   1. Equipment.

      1. Type.

         1. Included in initial qualifications:

            1. New equipment for the specific coating.

            2. Not previously qualified equipment for the specific coating.

         2. Not included in initial qualifications:

            1. Dust collectors.

            2. Turntables.

            3. Manipulators.

            4. Air jets.

      2. Test (use a qualified spray schedule).

         1. Sprayability.

            1. Metallography.

            2. Hardness test, if applicable.

         2. Sprayability testing on:

            NOTE

            Plasma spray coating families include dimensional restoration coatings, wear resistance coatings, bond coatings, abradable coatings, and thermal barrier coatings.

            1. One of each coating family as a minimum.

            2. One of the three standard base materials as a minimum.

         3. Tensile bond testing (optional).

   2. Operator.

      1. For a new operator or new operator skill level, the qualification requirements are as follows:

         1. The machine operator (that is, the coating operator who uses automated equipment) must know metal spray theory and practical examination.

         2. The manual sprayer (that is, the coating operator who uses manual or semi-automated equipment) must take extensive training course(s) with examinations on theory, practice, and on-the-job-training (OJT).

         3. The programmer/operator (that is, the coating process programmer for robots, CNC machines) must take extensive training course(s) to the manual sprayer qualification requirements with additional training in spray equipment programming.

            NOTE

            Commercially available courses/training are:

            1. European Welding Federation (EWF) - European Thermal Spray Course.

            2. American Welding Society (AWS) - Performance Qualification Testing.

      2. The repair facility must supply the training to meet the operator skill requirements, by the methods as follows:

         1. On-the-job-training (OJT).

         2. Theoretical and practical courses and examinations.

         3. Process equipment programming.

   3. Coating.

      1. For new coating, new powder (manufacturer or product number), or new spray process parameters, examine the coating by these tests:

         1. Sprayability test (uses a flat panel).

            1. Metallography.

            2. Hardness test, if applicable.

         2. Tensile bond test.

            1. Test the bond on each standard base material.

   4. Part (Engine Component Being Repaired) - Qualification Of A Coating On A New Part.

      1. Evaluate the coating on the engine part to the repair requirements and establish the correlation with process test coupons.

         1. Test coupons must be fully representative of the coating repair process.

            1. The test coupon alloy must be representative of the engine part alloy that is to be coated.

            2. The test coupon configuration must be representative of the engine part to be coated.

            3. The test coupons must be held in a fixture similar to the engine part to be coated.

         2. For a representative engine part for metallurgical evaluation, use one of these types of parts:

            1. A scrap part with a coated area representative of the repair.

            2. A simulated part with these features:

               1. A similar geometry.

               2. A representative alloy. See Table 1 (in Step) for representative materials/alloys for test panels and bond strength specimens).

               3. A coating area representative of the repair.

         3. Coating requirements include:

            1. Coverage.

            2. Thickness.

            3. Metallographic structure.

            4. Hardness test, if applicable.

3. SUBTASK 70-34-03-860-104 Re-qualification

   1. Equipment.

      1. Re-qualification of equipment is necessary when significant changes are made to the equipment.

         1. Significant changes include, but are not limited to:

            1. Controller.

            2. Gun.

            3. Cooling system.

            4. Rectifier.

            5. Significant re-calibration of process controls.

            6. Equipment relocation.

               NOTE

               Use a qualified plasma spray schedule.

      2. Necessary Tests.

         1. Sprayability test (use a flat panel).

            1. Metallography.

            2. Hardness test, if applicable.

            3. Sprayability test on one of each coating family as a minimum.

            4. Sprayability test on one of the three standard base materials as a minimum.

            5. Tensile bond test (optional).

   2. Operator.

      1. Active operators must re-qualify every two years.

      2. Operators inactive for six consecutive months must get re-qualified.

      3. Re-qualification by skill level is as follows:

         1. For the machine operator, successful examinations on theory and practice.

         2. For the manual sprayer (manual spraying or semi-automatic), successful examinations on theory and practice.

         3. For the programmer/operator (CNC- and PC-assisted spraying), successful examinations on theory and practice.

   3. Coating.

      1. Re-qualify coating spray schedules at least one time each year for all materials being sprayed on specific spray equipment.

         1. Re-qualification frequency can be extended when SPC (Statistical Process Control), or equivalent, is used.

      2. Necessary Tests.

         NOTE

         Use a flat panel.

         1. Sprayability test.

            1. Metallography.

            2. Hardness test, if applicable.

         2. Sprayability test on at least one of the three standard base materials.

   4. Part.

      1. Part re-qualification is necessary when the coating failed inspection.

         1. If an assignable cause for the failure can be identified that is outside the qualified process parameters, do the test again.

         2. If the test results are satisfactory, no re-qualification is necessary.

      2. Part re-qualification is necessary if the process coupon is visually or dimensionally unsatisfactory to correlate with the repair coating.

         1. If the root cause for the rejection can be identified and no process change is necessary, do the test again.

         2. If the results are satisfactory, no re-qualification is necessary.

4. SUBTASK 70-34-03-860-105 Periodic or Routine Qualification Tests

   1. Equipment.

      1. Test at intervals of time to make sure that each equipment set-up works satisfactorily. Do this test:

         1. Sprayability test (use a flat panel).

            1. Metallography.

            2. Hardness test, if applicable.

   2. Part.

      1. Test at intervals of time to make sure of continued quality and to agree with the SPC (Statistical Process Control) or quality plan.

      2. Test the scrap part or representative test piece by:

         1. Metallography.

         2. Hardness test, if applicable.

   3. Operator.

      1. Test at intervals of time to make sure that the operator's work is satisfactory.

   4. Powder.

      1. Test the individual batches of powder at intervals of time to make sure of continued quality and to agree with the SPC (Statistical Process Control) or quality plan by:

         NOTE

         Use a flat panel.

         1. Sprayability test.

            1. Metallography.

            2. Hardness test, if applicable.

5. SUBTASK 70-34-03-860-106 Quality Control Tests

   NOTE

   Test panel and bond strength specimens are to be representative of the process being qualified except it is necessary to use No. 60 alumina grit for bond specimen preparation.

   1. Test Materials.

      1. Test panel and bond test specimen materials are given in Table 1 (refer to Step) for the three general types of engine part materials.

         1. Metallographic Test of Panel Coating Thickness.

            1. Single coating thickness for metallographic evaluation should be between 0.008 and 0.012 inch (0.204 and 0.304 mm).

            2. For IAE 53-33, the coating thickness must be equivalent to the part thickness.

            3. Duplex (two-layer) coating thickness for metallographic evaluation should be between 0.003 and 0.008 inch (0.077 and 0.203 mm) for the bond coat and between 0.008 and 0.012 inch (0.204 and 0.304 mm) for the topcoat.

   2. Bond Strength Test.

      1. Coating Thickness for Bond Strength Test (See Table 2 in Step).

         NOTE

         IAE configuration is the type shown in Figure and Figure.

      2. Specimen Configuration.

         1. Coating.

            1. Spray directly onto specimens or onto buttons.

         2. Substrate (Bond Bar).

            1. Pinned grip (see Figure for Type 1A.).

            2. Threaded grip - internal or external (see Figure for Type 1B.).

            3. Button-pinned or threaded grips (see Figure for Type 2A and Figure for Type 2B.).

         3. Substrate Preparation.

            1. Clean the test pieces by the same process as you use on parts.

               NOTE

               When you touch the test piece, use the same care and methods that you use on the engine parts.

            2. Blast with No. 60 grit alumina to get a matte finish. Blast parameters must be representative of the production process.

         4. Coating of Bond Bars.

            1. Process Parameters.

               1. Torch spray angle must be 90 degrees +/- 10 degrees.

               2. All other parameters must be the same as the process being qualified.

            2. Equipment can be manual or automated.

         5. Coating Thickness Control.

            1. Measure coated specimens with a calibrated ball micrometer.

               NOTE

               It is necessary to include an uncoated control test specimen (dummy) along with the actual test specimens to make sure that the adhesive is satisfactory.

      3. Bonding.

         1. Adhesives.

            1. Adhesives (2500 psi (17236.9 kPa) minimum strength) for abradable and porous coatings are:

               1. CoMat 08-157 ADHESIVE.

               2. CoMat 08-158 ADHESIVE FILM - EPOXY,SCRIM SUPPORTED.

               3. CoMat 08-158 ADHESIVE FILM - EPOXY,SCRIM SUPPORTEDA.

            2. Adhesives (8000 psi (55158.1 kPa) minimum strength) for all other coatings are:

               1. CoMat 08-156 ADHESIVE.

               2. CoMat 08-157 ADHESIVE.

               3. CoMat 08-159 ADHESIVE.

               4. CoMat 08-160 ADHESIVE.

               5. CoMat 08-161 ADHESIVE.

               6. Other OEM-approved equivalents.

         2. Bonding Test Bars.

            1. Prepare dummy substrate by:

               1. Solvent wipe (or equivalent).

               2. Grit blast with No. 60 grit or finer alumina.

            2. Alignment.

               1. V-block (or equivalent) method.

            3. Adhesive Cure Cycle.

               1. Refer to the manufacturer's requirement.

            4. Cured Adhesive Edge Clean Up.

               1. Use any method that removes excess adhesive and coating by abrasion on the sides of specimens.

               2. The method must not significantly change the test bar geometry.

            5. Coated Test Bar Surfaces.

               1. Light sanding of the coated surface to remove loose particles is permitted.

      4. Test.

         1. Use Tensile Test Equipment with 20.000 psi (140 MPa) minimum capability.

         2. Test to the procedure in ASTM C-633.

         3. Number of Test Specimens.

            1. Not less than three specimens for each coating/substrate combination in one test group.

            2. Not less than one uncoated control test specimen (dummy).

      5. Data Analysis.

         1. Record Test Failure Mode.

            1. Record of failure location, percent coating, and adhesive failure is optional but is suggested to help in trend analyses.

         2. Record Tensile Strength At Failure.

      6. Test Evaluation And Disposition Criteria.

         1. Valid Test.

            1. One hundred percent rupture through the coating.

            2. One hundred percent rupture through the epoxy above the minimum bond strength.

            3. Any rupture through the coating or coating and epoxy above the minimum bond strength.

         2. Invalid Test.

            1. One hundred percent epoxy failure at less than the minimum bond strength.

         3. Pass.

            1. All valid data points in one test group must meet the Standard Practices/Processes Manual (SPM) minimum regardless of the failure location.

         4. Fail.

            1. Any individual data point that does not agree with the Standard Practice/Processes Manual minimum regardless of the failure location.

         5. Re-test if the test was invalid.

            1. Do not re-test the same samples.

            2. New specimens are necessary.

            3. It is recommended that the same coating parameters be re-tested.

         6. Re-test if the test was failed.

            1. Do not re-test the same samples.

               NOTE

               It is recommended that the coating parameters be evaluated and adjusted to improve performance.

            2. New specimens are necessary.

         7. Frequency of Testing.

            1. Test by the Quality Control Program in SPM TASK 70-34-03-340-501-001, Plasma Coating Quality Control Tests.

   3. Metallographic Preparation.

      1. Equipment.

         1. Tooling to prepare metallographic samples.

            1. Section the samples with:

               1. Cut-off wheels.

               2. Diamond wire.

               3. High pressure waterjet cutting.

               4. Other suitable method.

            2. Cleaning materials and equipment.

               1. Solvents.

               2. Soap and water.

               3. Ultrasonics.

               4. Oven.

            3. Mounting equipment.

            4. Grinding/polishing equipment.

            5. Microscope.

            6. Other.

      2. Qualification/Certification of the Metallurgist/Metallographer/Equipment/Laboratory.

         1. For the preparation of the test specimens and the interpretation of photomicrographs, the operator must have considerable experience and practice, as well as full knowledge of the equipment available in a given laboratory.

         2. Because the metallographic equipment is a key component in the production and evaluation of the specimen, the equipment must undergo regular maintenance and calibration.

         3. The correct interpretation of the specimen is of greatest importance. The personnel who do these procedures and compare the results to standards, must have training to do these functions correctly. Thus, the supplier's quality system should include equipment maintenance and calibration as well as training for all metallographic personnel to correctly do all the necessary functions and analyses.

      3. Metallographic Preparation.

         1. General.

            1. Metallographic preparation of thermal spray samples includes the preparation of a composite specimen composed of the coating and substrate material. Coating types can vary from soft porous abradables to dimensional restoration metal build-ups to hardface materials. Many coatings with similar properties can be prepared by a universal standard method; but, there can be special considerations for materials at the soft or hard end of the spectrum. It is permitted to use methods developed for cast or wrought metallic samples for coatings with these two considerations:

               1. Coatings are more heterogeneous in nature than wrought and cast metals.

               2. Coatings are more sensitive to smearing and mechanical damage during preparation.

            2. Semi-automated or automated grinding/polishing equipment for thermal spray materials will improve repeatability and consistency as compared to polishing by hand.

         2. Microstructure Test Panel Size.

            1. Minimum panel size must be 1.5 inches (38.1 mm) long X 0.75 inch (19.05 mm) wide X 0.060 inch (1.524 mm) thick.

            2. If the minimum panel size is not possible, coated panels used for metallographic evaluation must be large enough to prevent edge effects.

         3. Sectioning.

            1. Many spray shops do not find sectioning necessary because they spray a small sample that can be mounted and then ground/polished to an applicable plane for review/interpretation.

            2. If sectioning is necessary, the two common methods are:

               1. Abrasive wheel cutting.

               2. Diamond wire cutting.

            3. Sectioning considerations.

               1. The spray direction can influence the metallographic result.

               2. Always section with the cut force from coating to substrate.

               3. The specimen must be cut through the width. Minimum separation between cuts must be 0.5 inch (12.7 mm).

               4. Use minimal clamping pressure, and, if possible, a soft cushion (for example wood) to secure the specimen for sectioning. This will minimize possible cracks in the coating and change to the structure.

               5. A thin sectioning wheel will minimize damage, which must be removed in subsequent steps.

               6. Apply minimum pressure during actual cutting to minimize possible overheating of the specimen and a change to the structure.

               7. Wheels that have a binder that breaks down easily to show fresh cutting surfaces are usually best for a wide range of coatings.

               8. For the choice of sectioning method, it is very important to keep written procedures and identify the critical parameters requiring control for consistent techniques.

         4. Cleaning.

            1. Remove all contamination from the surface of the specimen.

            2. Remove all fluids that penetrated the coating.

            3. Recommended methods can include one or more of these methods:

               1. Washing with soap and water.

               2. Brushing or soaking of sample in solvent-like materials (such as acetone/alcohol) followed by application of heat with possibly a heat gun or hot plate to drive off any internal absorption.

               3. Cleaning of sample with an initial/extra vacuum step (if you use a vacuum impregnation in mounting) to make volatile the material that is caught in the part.

               4. 

                  CAUTION

                  BE CAREFUL THAT YOU DO NOT CAUSE DAMAGE TO THE COATING MICROSTRUCTURE DURING ULTRASONIC CLEANING.

                  Ultrasonic cleaning can be used to remove contamination.

         5. Mounting.

            1. Mounting is very important as it adds to the integrity of the sample during grinding/polishing.

            2. Methods for mounting coated materials.

               1. Hot mounting (in a press). Use this method only if the characteristics that follow are not evaluated: Transverse cracks, delaminations, separation, and porosity.

               2. Cold Mounting (can be helped by heat, vacuum impregnation, or pressure impregnation).

            3. Typical mounting materials for coatings (see Figure).

               1. Hot Mount (epoxies or Bakelite).

               2. Cold Mount (epoxies).

            4. Considerations for the choice of mounting procedure/material.

               1. Time available for mounting.

               2. Size, frequency, and the degree of interconnected porosity in the coating.

               3. Necessary viscosity of epoxy for impregnation of porosity, if important.

               4. Hardness of coating compared to the hardness of the mounting material.

            5. For porous coatings (such as, abradables, thermal barrier coatings (TBC), and other materials), cold mounting with vacuum impregnation alone and/or pressure impregnation is recommended. The viscosity of the cold mount epoxy will be important if the porosity in the coating is small and is not easy to impregnate.

            6. A well-impregnated sample will also show fewer tendencies towards pullout of phases and microstructure damage.

            7. For the choice of mounting method/material, it is very important to keep written procedures and identify the critical parameters necessary for the control of consistent techniques.

         6. Grinding and Polishing.

            1. There are many methods/formats available for the preparation of coating samples. The primary items include the usual grinding papers and the newer disc systems.

            2. The critical parameters that must be considered /controlled in preparation are given in Table 3 in Step.

         7. Considerations for the choice of preparation method for a coating type.

            1. Material removal rate.

            2. Hardness of the coating compared to the abrasive type.

            3. Tendency of coating phases to be pulled out.

            4. Composition of coating phases to prevent chemical attack.

            5. Degree of impregnation from the mounting.

            6. Tendency of smearing (closing porosity).

            7. Sample size.

            8. Tendency of the coating to crack.

            9. Edge retention.

         8. During the initial grinding, carefully remove the cut-off damage if the sectioning step was used. If an as-sprayed coupon is used, it is necessary to remove sufficient material to prevent coating edge effects.

         9. 

            CAUTION

            BE CAREFUL TO PREVENT OVERPOLISHING IN THE FINAL STEPS OF PREPARATION.

            Polishing formats for coatings usually include moderate to extended times on no nap cloths followed by short finishing steps on higher nap cloths.

         10. Typical procedures that include both grinding paper and disc formats are shown in Tables 4 and 5 in Step. These procedures will require modification for different coating types and equipment available in the specific laboratories.

         11. Equipment is available that will control some or all of the critical parameters. These semiautomatic/automatic machines together with written procedures that monitor/control critical parameters will give consistent and reproducible results.

             1. Regular calibration and maintenance of the equipment will help to give reliable results.

         12. Repolishing and regrinding of metallographic samples can be necessary if the metallographic preparation process causes a rejectable (unsatisfactory) condition.

      4. Consumables.

         1. Consumables used in the metallographic process are very important to the end result. It is important to use high quality materials to be sure that you get reproducible and consistent results.

         2. Although consistency from a reliable manufacturer is usually good, products from company to company can vary due to lack of standards within the industry. Changes in consumable suppliers should be carefully considered.

         3. If changes are made to an already established procedure with new consumables, it is recommended that some trial samples be run to make sure you get similar performance and results. Some examples of material variability are as follows:

            1. The amount of grit deposited on a grinding paper can vary and can cause removal differences during grinding.

            2. The amount of diamond in a suspension, its shape and particle size, and distribution can result in rates of removal that change during polishing.

            3. Changes in the type of carrier in a suspension can have an effect on the material removal rate and performance of the grinding paste. This can also have an effect the corrosion potential of the solution.

      5. Use of Physical Metallographic Standards.

         1. A relatively new concept is the use of metallographic standards to understand the reliability of metallographic equipment and consumables. These standards can be used in the same way calibration blocks are used to test the repeatability of hardness machines. The microstructure of these standards must be fully documented before their use in this exercise. By polishing a sample of known quality, a comparison can be made between the new metallographic process and the old and accepted process. If there are little or no differences in the old and new processes, it is permitted to use the new metallographic process. Typical situations where this new procedure is used are:

            1. Periodic sampling, self-auditing, or a machine not used for an extended period of time.

            2. Metallographic results that show a harmful change to the coating with no known cause connected to the spray process.

            3. Introduction of new consumables, equipment, or grinding/polishing methods.

      6. Microhardness.

         1. Some characteristics of thermal spray coatings (for example, pores, splat boundaries, and phases) can have an effect on hardness readings.

         2. Use the subsequent steps to make sure that the hardness values represent the coating's true properties. (Refer to RULE 14 in Rules for Metallographic Examination in Step.).

            1. For homogeneous coatings (one phase or constituent), it is usually possible to evaluate the coating with a load lighter than the load used for coatings that are less homogeneous.

            2. Hardness impressions are less accurate in areas where the coating does not have its usual qualities, as on coating edges, interfaces and surfaces with unusual inclusions (for example, large pores or unmelted particles).

            3. The size of the hardness impression must be sufficiently large to be typical of the coating microstructure and not any specific phase.

            4. If the coating thickness specified is less than that which will make it possible to do a satisfactory microhardness inspection, apply the coating to a sample to a thickness sufficient for the hardness test. (See RULE 3 in Rules for Metallographic Examination in Step).

      7. Metallographic Definitions For Coated Test Samples.

         1. Coating Contamination: Unwanted (foreign) material present in the coating.

            1. This contamination can be in the form of metallic or ceramic particles. These particles can come from sources such as nozzle hardware and contaminated power feed systems. See Figure.

         2. Crack: A linear or branched separation with a general perpendicular direction within the coating. See Figure.

         3. Delamination: A separation or horizontal defect that follows, or is associated with, the contour of the laminar build-up of the coating layers. See Figure.

            1. For linear interface defects, refer to Separation.

         4. Integrity: The overall quality and soundness of the coating. The integrity of a coating with only one defect (for example, oxide clusters, massive porosity, or unmelted particles) can be considered acceptable (satisfactory) but integrity can become considered rejectable (unsatisfactory) if there are more than one of these defects. Coatings are also considered rejectable (unsatisfactory) that have excessive segregation or an uneven distribution of defects, phases, or coating components. Individually, these features could be within their metallographic limits, but, when concentrated in a localized area, could become a possible problem. See Figure.

         5. Interface Contamination: Embedded unwanted (foreign) particles or contamination between the base metal and the coating. This contamination can be in the form of oxides, grit, or coating remaining from previous stripping operations. See Figure.

            NOTE

            It is very important for all personnel to know that there can be size differences between the photographic field of view and the microscopic field of view.

         6. Field of View (FOV): A unit area as viewed or photographed with normal light microscopy. Used as a unit of measure to help determine the percent that a particular feature or condition occurs. To examine specific rejectable (unsatisfactory) conditions, count the affected number of fields of view. Fields of view must not overlap and must be of random selection.

         7. Frequency Of Occurrence: Coating conditions and how frequent they are have these definitions:

            1. Negligible.

               1. Less than 1 percent.

               2. A one time occurrence or a condition that occurs in quantities that are too small or too few to measure.

            2. Isolated.

               1. 1 to 5 percent.

               2. A condition that occurs in a very small number of locations.

            3. Occasional.

               1. Greater than 5 percent to 16 percent.

               2. A condition that occurs in a small number of locations and at intervals that are not frequent.

            4. Intermittent.

               1. Greater than 16 percent to 40 percent.

               2. A condition that occurs in a moderate number of locations and at intervals that are frequent.

            5. Predominant.

               1. Greater than 40 percent to 90 percent.

               2. A condition that occurs in a large number of locations and at intervals that are very frequent.

            6. Predominant.

               1. Greater than 40 percent to 90 percent.

               2. A condition that occurs in a large number of locations and at intervals that are very frequent.

            7. Continuous.

               1. Greater than 90 percent to 100 percent.

               2. A condition that occurs fully (completely) or almost fully (completely) (that is, with no interruptions or with only isolated interruptions). This condition applies to linear-type conditions only (for example, interface conditions).

         8. Lack of bond: Refer to Separation.

         9. Layering: Stratification of coating components or features. See Figure.

         10. Massive Porosity: A large pore (hole) or a cluster of small pores (holes) in a specific area. See Figure.

         11. Multilayer coating: Two or more coating material layers, typically a bondcoat and topcoat with or without an intermediate coating layer.

         12. Oxide Clusters: Concentration of oxides. See Figure.

         13. Oxide Stringers: Wavy oxide striations that run parallel through the coating. See Figure.

         14. Oxides: Oxidized coating constituents.

         15. Porosity: Holes within a coating.

         16. Powder Particle Size is:

             1. Coarse powders: Coarser than +325 mesh (ASTM E11).

             2. Fine Powders: -325 mesh or finer.

         17. Pullout: Mechanical damage associated with metallographic preparation.

         18. Separation: A defect that follows or is associated with the contour of the interface. See Figure. For linear intra-coating defects, refer to Delamination.

         19. Straight-line Interface: A condition associated with insufficient roughening of the surface before spraying.

         20. Uniformity: Distribution of constituents (such as, phases, porosity, oxides). See Figure.

         21. Unmelted Particles: Unreacted powder particles contained within the coating matrix. These particles have a globular or angular appearance, are not adhered to the adjacent coating matrix, and are not part of a cohesive microstructure. See Figure.

      8. Magnification for Metallographic Examination.

         1. View the polished surface at either 500X or 200X magnification, as necessary, and evaluate by the acceptance standards in SPM TASK 70-34-03-340-501-002.

      9. Equipment for Metallographic Examination.

         1. Equipment, applicable for this operation and that gives up to 500X magnification, is available from the subsequent Supplier Code. Refer to V2500-00-00-00-00-00A-00KA-D for the company name/address identified by this number:

            1KGE8.

      10. Hardness Test (IAE 53-1, -5, -10, -16, -38, and -69 Coatings).

          1. Mount the test specimen in the microhardness tester. A list of test equipment is available from the subsequent Supplier Code. Refer to V2500-00-00-00-00-00A-00KA-D for the company name/address identified by this number:

             80140.

          2. Complete the microhardness test as specified in the Microhardness step in the Metallographic Preparation and Examination section.

          3. Record the data: minimum, maximum, and average hardness. Refer to SPM TASK 70-34-03-340-501-002.

6. SUBTASK 70-34-03-860-107 Rules for Metallographic Examination

   NOTE

   Coating-specific acceptance standards must supersede the Rules.

   1. RULE 1 - Five percent Rule, as applicable to Field of View (FOV): Five percent of all Fields of View can show unacceptable (unsatisfactory) coating characteristics but not cause the rejection of the coating.

      1. Applicable to:

         1. Unmelts.

         2. Oxides.

         3. Porosity.

         4. Phases.

         5. Uniformity.

         6. Interface Contamination.

      2. Not applicable to:

         1. Separation.

         2. Delamination.

         3. Cracks.

         4. Oxide Clusters.

   2. RULE 2 - Coating Contamination (Refer to the applicable quality standard in SPM TASK 70-34-03-340-501-002 for Acceptance Standards.).

   3. RULE 3 - Coating Thickness requirements:

      1. Single layer coatings must be 0.008 to 0.012 inch (0.204 to 0.304 mm) thick.

      2. Duplex (two-layer) coatings must be 0.003 to 0.008 inch (0.077 to 0.203 mm) for the bond coat and 0.008 to 0.012 inch (0.204 to 0.304 mm) thick for the topcoat.

   4. RULE 4 - Cracks (Transverse): Ratable if length is greater than 0.001 inch (0.025 mm). Do the inspection at 500X magnification. Any ratable condition is rejectable (unsatisfactory).

   5. RULE 5 - Delamination: Ratable if length is greater than 0.005 inch (0.127 mm). Do this inspection at 200X magnification. Any ratable condition is rejectable (unsatisfactory).

   6. RULE 6 - Edge Effects: Do not include coating that is less than 0.040 inch (1.016 mm) from the test piece edge or coating run out. (This rule is not applicable to part cut-ups.).

   7. RULE 7 - Field of Evaluation: The minimum area of coating necessary for evaluation minus edge effects.

   8. RULE 8 - Field of View (FOV): Fields of view must not overlap and must be of random selection.

   9. RULE 9 - Illumination: Use a bright field for comparison with photographic standards. Use Differential Interference Contrast (DIC) to increase the phase contrast during the evaluation.

   10. RULE 10 - "In-between" Condition: If the interpretation of any condition is between two criteria, report the condition as the worse condition.

   11. RULE 11 - Integrity: A coating is rejectable (unsatisfactory) if two or more acceptable (satisfactory) conditions combine to cause the coating to be unsound (weak) or not homogeneous.

   12. RULE 12 - Interface Evaluation:

       1. It is necessary to evaluate each interface in a multilayer coating system.

       2. Contamination can be in the form of oxides, grit, or any coating remaining from previous stripping operations.

       3. Do not include separation in the evaluation for interface contamination.

   13. RULE 13 - Massive Porosity:

       1. For coarse powder coatings: A pore or cluster of pores greater than 0.001 inch (0.025 mm).

       2. For fine powder coatings: A pore or cluster of pores greater than 0.0004 inch (0.010 mm).

   14. RULE 14 - Microhardness Requirements:

       1. Do not acquire hardness measurements within three (3) indication diagonals from the interface, coating edge, or surface.

       2. Indentations must be made on the coating cross-section and transverse the total available coating thickness.

       3. Microhardness testing must be done on metallographically prepared surfaces and include the average of five (5) or more impressions.

          NOTE

          IAE recommends that you make 10 or more indentations to get reliable CpK values.

       4. Use the heaviest load possible. This load must fit in the coating and meet the requirements of ASTM E-384 (also see RULE 6).

          NOTE

          RULE 1 does not apply.

   15. RULE 15 - Oxide Clusters: Ratable if the longest dimension is greater than 0.003 inch (0.076 mm) or 75 percent of the coating thickness, or the number of unratable clusters is greater than five (5) in one standard field of evaluation (see RULE 6). Any ratable condition is rejectable (unsatisfactory).

   16. RULE 16 - Repolishing: Limited to two. Use only for removal of damage that is a result of unsatisfactory preparation.

       NOTE

       Coating oxides and contamination must not be considered as interface separation.

   17. RULE 17 - Separation: Ratable if greater than 0.005 inch (0.127 mm) or if total of non-ratable lengths is more than six (6) percent of standard field of evaluation. Any ratable condition is rejectable (unsatisfactory).

   18. RULE 18 - Uniformity: Non-homogeneous distribution/dispersion of constituents is not acceptable (that is, is unsatisfactory). See RULE 11 - Integrity.

   19. RULE 19 - Unmelted Particles (Unmelts): Must be greater than 75 percent unbonded. Ratable if size aspect ratio is less than 3:2 (longest:shortest) or if the longest measured dimension is greater than 0.002 inch (0.051 mm) for coarse powder coatings or greater than 0.001 inch (0.025 mm) for fine powder coatings.

7. SUBTASK 70-34-03-860-108 Tables

   1. Table 1. Test Panel and Bond Specimen Materials

      Substrate Material		Alloy Specification
      Iron, or Nickel, or Cobalt based alloys		AISI 321SS AMS 5504, AMS 5613 Inco 718 Hastelloy X
      Titanium alloys		AMS 4901, AMS 4902, AMS 4921 AMS 4910, AMS 4926 AMS 4911, AMS 4928
      Aluminum alloys		Alloy 6061 Alloy 5052

   2. Table 2. Coating Thickness Requirements for Bond Strength Test

      Coating		Thickness, Inches (mm)
      IAE 53-11, -69		0.003 - 0.005 (0.077 - 0.127)
      IAE 53-1, -5, -16, -17, -38		0.006 - 0.008 (0.153 - 0.203)
      All Others		0.008 - 0.010 (0.204 - 0.254)
      IAE 53-33 (Includes Undercoat)		0.013 - 0.020 (0.330 - 0.508)

      NOTE

      When a bond strength test is specified for IAE 53-35 coating applied over an undercoat of IAE 53-21 or IAE 53-37, apply the undercoat to a thickness of 0.002 to 0.004 inch (0.051 to 0.101 mm); then add a top coat of IAE 53-35 for a total coating thickness of 0.008 to 0.010 inch (0.024 to 0.254 mm).

   3. Table 3. Critical Parameters for Grinding and Polishing

      Parameter		Description
      Pressure		Applied/specified for each mount
      Speed		Both table and specimen holder
      Rotation Direction		Relative rotation of head in relation to the table
      Format		Grinding: Disc compared to grinding papers Polishing: No nap compared to high nap cloths
      Type of Abrasive		Diamond, silicon carbide, colloidal silica, aluminum oxide
      Quantity of Abrasive		ml/min.
      Orientation		How samples are put in holder in relation to wheel rotation
      Frequency		How often lubricant/abrasive is applied
      Type of Lubricant		Oil, water, alcohol
      Quantity of Lubricant		ml/min.
      Time		Total for individual steps

   4. Table 4. Typical Preparation Procedure for Abrasive Papers

      Surface	Abrasive, Grit Size Lubricant	Load/ Specimen	Speed (RPM)	Time	Rotation
      Grinding Papers or Grinding Stone	SiC 120 or 180 Water	5 lbs. (2.27 kg)	300	Enough papers to flatten specimen and remove damage/edge effects; 30 seconds	Complimentary
      Grinding Papers	SiC 240 thru 800/1200 Water	5 lbs. (2.27 kg)	300	Usually two papers/grit size; 30 seconds	Complimentary
      No Nap Cloth	Polycrystalline or monocrystalline diamond Can be in the range 1 to 6 micron diamond Water or Alcohol	5 lbs. (2.27 kg)	300	Can be in the range of 1 to 4 minutes	Complimentary
      Higher Nap Cloth	Colloidal silica, aluminum oxide (used to prevent overpolishing) Usually 0.05 micron Water or Alcohol	5 lbs. (2.27 kg)	300	Usually 15 to 30 seconds	Complimentary

   5. Table 5. Typical Preparation Procedure for Abrasive Discs

      Surface	Abrasive, Grit Size Lubricant	Load/ Specimen	Speed (RPM)	Time	Rotation
      Grinding Stone	SiC 120 or 180 Water	5 lbs. (2.27 kg)	300	Enough to flatten specimen and remove damage/edge effects; 30 seconds	Complimentary
      Fixed Diamond or Composite Disc	Polycrystalline or monocrystalline diamond 40 to 60 micron Water	5 lbs. (2.27 kg)	300	Enough to flatten specimen and remove damage/edge effects; 2 to 4 minutes	Complimentary
      Fixed Diamond or Composite Disc	Polycrystalline or monocrystalline diamond 6 to 9 micron Water	5 lbs. (2.27 kg)	300	3 to 5 minutes	Complimentary
      No Nap Cloth	Polycrystalline or monocrystalline diamond Can be in the range 1 to 6 micron diamond Water or Alcohol	5 lbs. (2.27 kg)	300	Can be in the range 1 to 4 minutes	Complimentary
      Higher Nap Cloth	Colloidal silica, aluminum oxide (used to prevent overpolishing) Usually 0.05 micron Water or Alcohol	5 lbs. (2.27 kg)	300	Usually 15 to 30 seconds	Complimentary

   6. Table 6. Key to Figure IAE Bond Strength Specimen

      1	0.88 Inch (2.235 mm) diameter maximum. (No. 2 center drill ref) Depth 0.110 inch (2.794 mm) maximum. Chamfer 60 deg +/- 6 deg included to 0.120 Inch (3.048 mm) diameter maximum (optional).
      2	Chamfer to 0.050 to 0.080 inch (1.27 to 2.03 mm) X 45 deg approximately.
      3	1.500 to 2.250 inches (38.1 to 57.2 mm)
      4	1.000-12 UNF-3A, Pitch diameter 0.9415 to 0.9459 inch (23.915 to 24.025 mm). Major diameter 0.9886 to 0.9905 inch (25.111 to 25.158 mm). Minor diameter 0.8978 inch (22.804 mm) maximum.
      5	Vibration peen identification in shaded area.
      6	Coat this end. Surface "A" must be square with centerline within 0.001 inch (0.025 mm) FIR before coating. This is a critical requirement.
      7	0.960 to 0.990 inch (24.38 to 25.15 mm) diameter.
      8	No overspray is permitted. Mask outside diameter of specimen.
      9	1.00 inch (25.400 mm) maximum. Full or imperfect thread.
      10	0.834 Inch (21.184 mm) minimum full thread.

   7. Table 7. Key to Figure IAE Universal Adaptor To Attach Bond Test Specimen To Tensile Test Equipment

      1	1.000-12 UNF-3B to fit bond test specimen
      2	0.005 inch (0.127 mm) clearance
      3	To fit tensile test machine

      Table 8. Key to Figure Other Bond Strength Specimen Configurations

      1	0.39 - 0.40 inch (9.91 - 10.16 mm) diameter
      2	0.16 - 0.24 inch (4.06 - 6.10 mm) radius
      3	0.386 - 0.402 inch (9.80 - 10.21 mm)
      4	1.96 - 1.98 inches (49.78 - 50.29 mm)
      5	1.33 - 1.35 inches (33.78 - 34.29 mm)
      6	0.66 - 0.68 inch (16.76 - 17.27 mm)
      7	0.98 - 0.99 inch (24.89 - 25.15 mm) diameter
      8	90 +/- 2 deg

      Table 9. Key to Figure Other Bond Strength Specimen Configurations (2)

      1	0.99 - 1.00 inch (25.15 - 25.40 mm) diameter
      2	1.90 - 2.10 inches (48.3 - 53.3 mm)
      3	1.125 inches (28.575 mm) maximum
      4	1.00 inch (25.40 mm) - 8NC - 2A diameter
      5	0.50 inch (12.70 mm) - 20 UNF - 2B (minimum) diameter; 0.625 inch (15.875 mm) - 18 UNF - 2B diameter; 0.75 inch (19.05 mm) - 16 UNF - 2B (maximum) diameter

      Table 10. Key to Figure Other Bond Strength Specimen Configurations (3)

      1	0.39 - 0.40 inch (9.91 - 10.16 mm) diameter
      2	0.16 - 0.24 inch (4.06 - 6.10 mm) radius
      3	0.386 - 0.402 inch (9.80 - 10.21 mm)
      4	0.12 - 0.28 inch (3.0 - 7.1 mm)
      5	1.96 - 1.98 inches (49.78 - 50.29 mm)
      6	1.33 - 1.35 inches (33.78 - 34.29 mm)
      7	0.66 - 0.68 inch (16.76 - 17.27 mm)
      8	0.98 - 0.99 inch (24.89 - 25.15 mm) diameter
      9	90 +/- 2 deg

      Table 11. Key to Figure Other Bond Strength Specimen Configurations (4)

      1	0.99 - 1.00 inch (25.15 - 25.40 mm) diameter
      2	1.90 - 2.10 inches (48.3 - 53.3 mm)
      3	1.00 inch (25.40 mm) diameter - 8NC - 2A diameter
      4	0.50 inch (12.70 mm) - 20 UNF - 2B (minimum) diameter; 0.625 inch (15.875 mm) - 18 UNF - 2B diameter; 0.75 inch (19.05 mm) - 16 UNF - 2B (maximum) diameter
      5	1.125 inches (28.575 mm) - maximum
      6	0.245 - 0.255 inch (6.22 - 6.48 mm)

Figure: Specimen Configuration - IAE Bond Strength Specimen. For Key, Refer to Table 6.

Specimen Configuration - IAE Bond Strength Specimen. For Key, Refer to Table 6.



Figure: IAE Universal Adaptor To Attach Bond Test Specimen to Tensile Test Equipment. For Key, Refer to Table 7.

IAE Universal Adaptor To Attach Bond Test Specimen to Tensile Test Equipment. For Key, Refer to Table 7.



Figure: Other Bond Strength Specimen Configurations. For Key, Refer to Table 8.

Other Bond Strength Specimen Configurations. For Key, Refer to Table 8.



Figure: Other Bond Strength Specimen Configurations. For Key, Refer to Table 9.

Other Bond Strength Specimen Configurations. For Key, Refer to Table 9.



Figure: Other Bond Strength Specimen Configurations. For Key, Refer to Table 10.

Other Bond Strength Specimen Configurations. For Key, Refer to Table 10.



Figure: Other Bond Strength Specimen Configurations (4). For Key Refer to Table 11.

Other Bond Strength Specimen Configurations (4). For Key Refer to Table 11.



Figure: Examples of Hot and Cold Mounting Techniques on Smearing

Examples of Hot and Cold Mounting Techniques on Smearing



Figure: Examples of Coating Contamination

Examples of Coating Contamination



Figure: Example of Crack

Example of Crack



Figure: Examples of Delamination

Examples of Delamination



Figure: Examples of Poor Integrity

Examples of Poor Integrity



Figure: Examples of Interface Contamination

Examples of Interface Contamination



Figure: Example of Layering

Example of Layering



Figure: Example of Massive Porosity

Example of Massive Porosity



Figure: Examples of Oxide Clusters

Examples of Oxide Clusters



Figure: Examples of Oxide Stringers

Examples of Oxide Stringers



Figure: Examples of Separation

Examples of Separation



Figure: Examples of Uniformity

Examples of Uniformity



Figure: Examples of Unmelted Particles

Examples of Unmelted Particles