Preliminary Requirements

Safety Requirements

WARNING

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

Procedure

1. SUBTASK 70-31-07-310-001 Preparation

   
   CAUTION
   DO NOT USE ALUMINUM OXIDE TYPE ABRASIVES, SUCH AS ORDINARY EMERY CLOTH, FOR THIS OR ANY OPERATION ON SURFACES TO BE BRAZED. ALUMINUM IN ANY FORM HAS HARMFUL EFFECTS ON MOLTEN BRAZE METAL FLOW.

   1. Surface roughness.

      1. To help the molten braze wet the surfaces, on joints without nickel plate, a surface rougher than 60 microinches (0.0015 mm) is recommended but not necessary. If surfaces are prepared by abrasive blasting, use wet or dry Silicon Carbide or wet novaculite.

         1. The abrasive must be clean and always used for similar work.

         2. Do not use abrasives made of Aluminum or Titanium.

   2. Clean the surface.

      1. Surfaces to be brazed must be cleaned before the parts are assembled. Refer to the SPM TASK 70-31-20-310-501. There must be no dirt, grit, oil, grease or other unwanted material on the surface.

      2. Protect the cleaned parts from dust and other contamination.

      3. Wear clean gloves if you touch parts, tools or brazing material during assebly before brazing.

      4. If necessary, remove scale and oxidation from surfaces by an approved method.

   3. Nickel plating.

      1. Joints must be prepared by nickel plating as given in the SPM TASK 70-33-05-300-503 or SPM TASK 70-33-06-300-503 as applicable (Refer to Step).

2. SUBTASK 70-31-07-310-002 Filler Metal

   1. Refer to Step.

3. SUBTASK 70-31-07-310-003 Brazing Atmosphere

   
   CAUTION
   WHEN PROCESS 4 IS SPECIFIED, ALL THERMAL TREATMENTS ABOVE 1225 DEG F (663 DEG C) AFTER THE BRAZING OPERATION, MUST BE DONE IN A PROTECTIVE ATMOSPHERE FURNACE (SEE Step).

   1. Flux must not be used.

   2. Assembly must be held so that all brazing parts will be aligned after brazing. Tack welding of honeycomb parts to substrate parts is permitted. Welds must not be harmful to the final product.

   3. CoMat 03-253 COMPOUND, BRAZING STOP-OFF can be used on parts and fixtures to prevent the flow of brazing alloy into areas that are not approved for brazing alloy.

4. SUBTASK 70-31-07-310-004 Procedure

   1. A furnace must be used to heat parts for brazing.The parts must be heated to a temperature given in Step until the temperature and pressure in the furnace is stabilized. The temperature must then be increased quickly to the brazing temperature as given in Step.

   2. Brazing time must not be more than 30 minutes.

   3. Time at temperature starts when the lowest recording load thermocouple is at the low end of the tolerance band below the selected brazing temperature. Brazing time ends when the lowest recording load thermocouple is below the low end of the selected brazing tolerance band during the cool-down part of the cycle.

      NOTE

      Lagging thermocouples are load thermocouples which are below the selected temperature range but which still increase in temperature.

      Load thermocouplese are those thermocouples that directly monitor (check) part temperature.

      The brazing temperature range is the range of temperature from the low end of the tolerance band below the selected brazing temperature to the maximum permitted brazing temperature.

   4. If a brazing load has lagging thermocouples, you can hold the load within the selected brazing temperature range while the lagging thermocouples increase in temperature. Pre-braze hold time within the brazing temperature range must not be more than 30 minutes after 75 percent of the recording load thermocouples are within the brazing temperature range.

   5. 

      CAUTION

      COOLING RATES SPECIFIED BY THE ENGINE MANUAL MAY BE DIFFERENT FROM THE STANDARD PRACTICES/PROCEDURE MANUAL (SPM). ADHERENCE TO ENGINE MANUAL REPAIR INSTRUCTIONS SUPERSEDES THE SPM REPAIR INSTRUCTIONS.

      After brazing but before you touch the parts, decrease the temperature of the assemblies for a sufficient time to permit the filler metal to become a solid at a rate which will prevent cracks and minimize internal stress, distortion, oxidation, decarburization, and scaling.

   6. The brazing atmosphere must be kept until the parts have cooled to below the scaling temperature.

   7. Lower the temperature of alloys hardened by heat treatment at a rate not less than 35 deg F (19 deg C)/ minute to 1100 deg F (593 deg C) and not less than 15 deg F (8 deg C)/minute from 1100 deg F (593 deg C) to 1000 deg F (538 deg C). (When you use a vacuum furnace, you can add pure argon to get this rate.) Use any rate below 1000 deg F (538 deg C).

   8. Brazed joints can be brazed again with the initial brazing alloy. Do not do more than two more brazing cycles on each part.

5. SUBTASK 70-31-07-310-005 The Quantity of Braze Filler Necessary

   1. Joints must show a complete line of filler metal between the component parts use an agreed method to do this check.

   2. Refer to Step for coverage requirements.

6. SUBTASK 70-31-07-310-006 The Quality of Brazing

   1. Refer to Step for the acceptance limits for conditions that are a result of the brazing process and for conditions that are a result of the handling and processing of detail parts and finish machining.

   2. The surfaces of parts must have no pitting or burning and must be free of too much brazing alloy.

   3. Brazed joints must be solid, clean and have no defects which are dangerous to the function of assemblies.

7. SUBTASK 70-31-07-310-007 Microstructural Analysis of too Much Braze on Honeycomb Parts

   NOTE

   The inspection standards that follow can be used to make an analysis of the honeycomb microstructure if necessary.

   1. Refer to: Figure

      NOTE

      On test pieces, where four segments are not necessary to make sure that the brazing is constant, one thru four segments can be used as determined by supervision.

   2. Preparation.

      1. Four segments equally spaced around a part must be marked so that it can be cut. This mark must be done so that a view of the part to be inspected is at 90 degrees to the ribbon direction. (Refer to Figure.).

      2. Cut a segment with a thin abrasive wheel (AW-797, Manhattan 544 or equivalent), flush with Solution Code 177 to prevent chipping and burning. Refer to SPM TASK 70-32-08-320-501.

         1. Remove burrs with a belt sander.

         2. Remove grease and other contamination by the applicable procedures.

      3. Mount and polish the segment as follows:

         1. Mount the segment in a standard medium, such as heat setting epoxy. Evacuate the mount before it hardens.

         2. Grind the mounted segment with a 50-80 grit grinding stone or an 80 grit Silicon Carbide or Zirconia grinding paper.

         3. Wet grind with 120-600 Silicon Carbide paper (or equivalent) in a sequence of steps which will cause a metallographically equal surface. Steps of 120, 240, 400 and 600 will be satisfactory. Ultrasonic clean by the applicable procedure.

         4. 

            CAUTION

            DO NOT POLISH TOO MUCH AS EDGE ROUNDING, INCLUSION PULL-OUT, PORE EXAGGERATION AND OTHER DEFECTS COULD OCCUR.

            Polish the segment on medium-hard surfaced, non-napped cloth with 1.0 micron diamond paste and an oil lubricant such as CoMat 10-061 STODDARD SOLVENT. Ultrasonic clean by the applicable procedure.

         5. To remove small scratches or other remaining defects, polish with a mixture of 0.3 micron alpha alumina powder and water on a napped cloth, such as a Buehlers Metcloth.

      4. Etch lightly with Kallings etchant.

   3. Examination (see Figure).

      1. Examine each segment at a magnification of 50X for the number of cells with braze mushroom at the top of finished machined surfaces or at the top of non-machined surfaces. Refer to C and D in Figure as applicable.

         1. Braze mushrooms on more than 10 percent of the cells are not permitted.

      2. Measure the height of braze fillet (F) and/or the height of braze fill (E).

         1. Not more than five percent of the cells can exceed the brazing alloy fill limit of Step (b). Adjacent filled cells are not permitted except within 0.125 inch (3.175 mm) of an edge.

         2. A filled cell is one in which the brazing alloy fill is more than the lesser of one half the final machined cell height or 0.060 inch (1.524 mm).

      3. All heights of braze flow on the edge of honeycomb rows (A) are permitted.

      4. All heights of braze wicking between the welded cell walls (B) are permitted.

   4. Record and report the results.

      1. Record and report the total number of cells that you examined.

      2. Record and report the number and percent of cells that show braze mushrooms at the top of finish-machined or unmachined honeycomb surfaces.

      3. If there is too much braze on the edge of honeycomb rows (braze flow or braze wicking), record and report as: PERMITTED. Refer to Steps B. (3) and (4).

8. SUBTASK 70-31-07-310-008 Inspection of Brazed Honeycomb (Gravity Leak Test or Video Inspection System)

   NOTE

   1. This procedure is only for the inspection of new honeycomb installed by a repair, not for engine-run honeycomb.

   2. In this procedure, there are two methods of inspection which are alternates to one another: Method 1 - Gravity Leak Test and Method 2 - Video Inspection System. If the Engine Manual repair specifies the gravity leak check, it is permitted to use either method.

   1. Materials and equipment.

      1. A suitable tank or container to permit all or a section of the brazed honeycomb to be put fully in the test fluid or a sprayer to spray the test fluid into the honeycomb cells.

      2. Water-based test fluid.

         NOTE

         It is necessary to add one percent of CoMat 10-097 CORROSION INHIBITOR,(NON-NITRITE) or CoMat 01-208 CORROSION INHIBITOR or CoMat 10-099 CORROSION INHIBITOR,WATER SOLUBLE to the solution or the material will corrode when put in the solution.

         1. 200:1 mixture of tap water to CoMat 02-142 WETTING AGENT or a 2500:1 mixture of tap water to CoMat 01-183 WETTING AGENT FOR ACIDCLEANER.

         2. High intensity light: fiber optic adaptable.

            NOTE

            The fiber optic probe is available from the source that follows:

            Scantech, 1 Nod Road, Ridgefield, CT 06877 USA. Tel: (203) 438-8566 Fax: (203) 438-8566.

         3. Fiber optic probe: 0.028 or 0.051 inch (0.71 or 1.30 mm) diameter, as applicable to the size of the honeycomb for inspection.

            NOTE

            The video inspection system is available from the source that follows:

            Hi-Scope Systems Company, 10 McKinley Street, Closter, NJ 07624 USA. TEL: (877)-HISCOPE (in USA) or (201) 768-2810 (outside USA) Fax: (210) 768-3944.

         4. Video inspection system: HiScope Model KH-2200 with MX50Z probe, or equivalent.

   2. Definitions.

      1. UNBONDED CELLS - Cells not brazed to the base material.

      2. PERIPHERAL CELLS - The outer most continuous boundary of whole hexagonal cells. Incomplete cells or cells affected by a chamfer are not included. Incomplete cells or cells affected by a chamfer must not be counted as unbonded peripheral cells.

      3. CENTER CELLS - Any cells that are not peripheral cells. Unbonded center cells are the number of cells that the light source illuminates to determine the maximum number of unbonded cells permitted. Cell wall holes, braze line holes, split cell walls, and separated walls that agree with approved limits are not included.

   3. Procedure.

      1. Method 1: The Gravity Leak Test.

         1. Partially fill the gravity leak test tank or container with water-based test fluid (or spray on the solution).

            1. Do not use this water-based fluid on parts with a honeycomb height more than 0.800 inch (20.320 mm) or with a honeycomb size (cell diameter) less than 0.0156 inch (0.397 mm).

            2. When you spray on the water-based fluid, be sure there is sufficient fluid pressure to remove any air caught within the cells.

         2. Clean the brazed part, if necessary. Refer to the SPM TASK 70-11-03-300-503.

         3. Put the part fully in the fluid for 30 seconds.

         4. Remove any air caught in the honeycomb cells by one of the methods that follow:

            1. Spray the test fluid into the cells with a sufficiently pressurized hose.

            2. Tap the part lightly with an approved mallet that is not made of metal.

            3. Brush the surface with a brush.

            4. Apply a sufficient vacuum to remove air from the honeycomb.

         5. 

            CAUTION

            DO NOT TOUCH THE SURFACE OF THE HONEYCOMB FILLED WITH FLUID TO PREVENT INCORRECT TEST RESULTS.

            Permit the test fluid to fill the honeycomb cells.

         6. Remove the part from the test fluid and drain as follows for not less than five minutes:

            1. For rings and vane clusters: in a horizontal position.

            2. For segments: at approximately a 45 degree angle.

         7. Examine the honeycomb cells for remaining solution. A drop in fluid level in the cell(s) is the result of leakage from one cell to another through an unbrazed joint or hole.

            1. Braze areas that are not satisfactory (complete) must not be more than 15 percent of the honeycomb area.

            2. Cells without braze around the edges of honeycomb are not permitted.

            3. Refer to the Engine Manual repair section for any additional inspection requirements.

               NOTE

               For inspection of vanes only, this light probe inspection can be an alternate to the gravity leak test. If you use the light probe inspection method, it is necessary to probe every second row of cells either vertically or horizontally, as shown in Figure.

         8. Evaluate areas of possible chamfered or overhanging peripheral cell leakage to the applicable standard. Use a high intensity light and a fiber optic probe to check for light transmission from the cell(s) in which the probe is inserted.

         9. Put the part fully in cold water; then, flush fully with hot water to remove remaining leak test solution.

         10. If necessary, apply corrosion inhibitor. Refer to the SPM TASK 70-38-37-300-503.

      2. Method 2: The Video Inspection System (Alternate Inspection Method).

         1. Be sure the camera is vertical to the honeycomb surface and the lens is focused on points of light at the bottom of the honeycomb.

         2. Examine the honeycomb on the monitor and index the part in a way that gives full inspection coverage of the braze joint.

         3. If a single cell or area of cells is in question, use a fiber optic light probe to check for light transmission (disbond) from the cell(s) into which the probe is inserted.

         4. Evaluate the honeycomb areas to see if the areas agree with the requirements of the applicable Inspection Standard (Step).

9. SUBTASK 70-31-07-310-009 Visual Inspection of Honeycomb Details and Brazed Assemblies Used for Abradable Rubstrips

   NOTE

   This procedure is only for the inspection of new honeycomb installed by a repair, not for engine-run honeycomb.

   1. Lessons learned.

      1. Honeycomb details and assemblies that are not sufficiently clean are not permitted and are harmful to engine operation and cause foreign object damage (FOD).

   2. Acceptance limits.

      1. Parts are acceptable that agree with the limits of this standard.

      2. Conditions not specified in this inspection are not permitted.

      3. The visual acceptance standards in the SPM TASK 70-21-01-220-501 do not apply to this procedure; but, the General Instructions in the SPM TASK 70-21-01-220-501 do apply.

         NOTE

         This section specifies acceptance limits for unbonded brazed honeycomb cells along the braze line usually evaluated by a gravity leak test or video inspection method. Refer to Step.

         All imperfections above the braze line must be evaluated to the limits in Steps D. and E.

   3. Braze coverage.

      NOTE

      The definitions that follow apply to this inspection.

      1. Definitions.

         1. PERIPHERAL CELLS: The outer most continuous boundary of whole hexagonal cells. Overhanging/incomplete cells or cells affected by a chamfer are not to be included. See Figure.

         2. CENTER CELLS: All remaining whole cells not defined as peripheral cells. See Figure.

            NOTE

            The limits that follow apply after a visual inspection occurs for the braze condition (such as, braze stain and line of braze) between the honeycomb and the mating part.

      2. General limits peripheral cells (applicable to all parts, full rings and segments).

         1. Overhanging/incomplete cells or cells affected by a chamfer must not be counted as unbonded peripheral cells.

         2. Braze line holes less than half the face width must be ignored. See Figure.

         3. Three braze line holes greater than half the face width but less than the full face width are permitted in any linear inch (25.4 mm). See Figure.

      3. Full ring assemblies.

         1. Peripheral cells.

            1. The general limits given in Step (2) apply.

            2. For the maximum number of unbonded peripheral cells permitted in any 5 inches (127 mm) of peripheral length, see Step.

            3. Local disbond, minor pin hole voids, or loss of bond at the peripheral cells, up to 50 percent of any honeycomb segment (if the disbond does not exceed half of the cell width), is permitted. See Figure.

               NOTE

               Unbonded center cells are expressed as "numbers of cells" and are based on an 85 percent minimum bond.

               It is permitted to do inspection to limits other than "number of cells", if you follow the limits of this standard.

         2. Center cells.

            1. For the maximum number of unbonded center cells permitted in any 2 square inch (12.9 square centimeter) area, see Step.

            2. Unbond must not extend across the full width of the honeycomb.

      4. Segmented assemblies.

         1. Peripheral cells.

            1. Special instructions.

               1. Limits for unbonded peripheral cells are given in Step and are based on the peripheral length of the examined part. To calculate the peripheral length, see Figure and Figure and the instructions that follow.

                  1. Figure is for narrow segments that have a width of five staggered rows or less. For these narrow segments, unbonded cells are only permitted along the top and bottom lengths. Unbonded cells are not permitted on the ends. Therefore, to calculate peripheral lengths, use only the top and bottom lengths.

                  2. Figure is for wide segments that have a width of more than five staggered rows. For these wide segments, unbonded cells are permitted along all four sides. Therefore, use all four sides to calculate peripheral lengths.

            2. Segment inspection sequence is as follows:

               1. Determine part type: narrow or wide.

               2. Calculate the peripheral length. See Figure or Figure, as applicable.

               3. Evaluate the part. See Step.

            3. General limits given in Step (2) apply.

            4. For assemblies with at least 5 inches (127 mm) of peripheral length, see Step.

            5. For assemblies with less than 5 inches (127 mm) of peripheral length, use Step to calculate (prorate) the maximum number of unbonded cells.

            6. Apply Step limits for unbond of peripheral cells as follows:

               1. For segments that have a total width of five staggered rows or less, no unbonded cells are permitted on either segment side. To calculate the peripheral length, use only the top and bottom honeycomb lengths. In Figure the total peripheral length is 4.000 inches (101.6 mm).

               2. For segments that have a total width of more than five staggered rows, use all four sides to calculate the peripheral length. In Figure, the total peripheral length is 12 inches (304.8 mm).

            7. Local disbond, minor pin hole voids, or loss of bond at the peripheral cells, up to 50 percent of any honeycomb segment (if the disbond does not exceed half of the cell width), is permitted. See Figure.

         2. Center cells.

            1. For all segmented parts: Within a 0.500 inch (12.700 mm) zone on each segment end, at least 50 percent of the center cells must be bonded. See Figure.

            2. Where the center area is at least 2 square inches (12.9 square centimeters), the maximum number of permitted unbonded center cells is given in Step.

               1. Unbond must not extend across the full width of the honeycomb.

            3. Where the center area is less than 2 square inches (12.9 square centimeters), calculate (prorate) the maximum number of unbonded center cells based on Step.

               1. Unbond must not extend across the full width of the honeycomb.

                  NOTE

                  Section I gives acceptance limits for conditions that are a result of the braze process.

   4. After braze inspection of honeycomb above the braze line - Section I.

      NOTE

      The definitions that follow apply to this inspection.

      1. Definitions.

         1. FILLED CELLS: Honeycomb cells in which the brazing alloy fill exceeds the lesser of one half the final cell height or 0.060 inch (1.524 mm).

            EXAMPLE: If cell heights are 0.120 inch (3.048 mm) or less, braze fill over one half of the cell height are filled cells.

            EXAMPLE: If cell heights are over 0.120 inch (3.048 mm), braze fill over 0.060 inch (1.524 mm) are filled cells.

      2. Cell wall holes.

         1. Cell wall holes are permitted on 50 percent of peripheral cells if there is no more than one hole in a cell and they are no larger than one-half the face width. See Figure.

            Exception: For 0.031 inch (0.787 mm) cell sizes, cell wall hole sizes are waived. It is permitted to evaluate holes as deformed cells (incomplete or damaged walls).

         2. Three cell wall holes greater than the half face width but less than the full face width are permitted in any linear inch (25.4 mm) if 50 percent of the peripheral cells are not affected and there is no more than one hole in each cell. See Figure.

      3. Filled cells.

         1. For acceptance limits for the maximum number of filled cells permitted for each part, see Step.

            1. Separations between filled cells must be as follows:

               1. Peripheral cells (all sizes): Filled cells can be adjacent to each other.

               2. Center cells (all sizes): Filled center cells must be separated by at least one unfilled cell. Filled center cells and peripheral cells can be adjacent to each other.

               3. For 0.031 inch (0.787 mm) cell sizes, filled center cells can be adjacent to each other in groups if there are no more than three adjacent cells along the circumferential length and no more than five adjacent cells across the axial width.

            2. Where the total honeycomb area is at least 4 square inches (25.8 square centimeters), see Step for the total number of permitted filled cells for each part.

            3. Where the total honeycomb area is less than 4 square inches (25.8 square centimeters), see Step to calculate (prorate) the total number of permitted filled cells in a part.

               NOTE

               Section II gives acceptance limits for conditions that are a result of the handling and processing of detail parts and finish machining. These limits must be used to accept assemblies and/or detail parts.

   5. After braze inspection of honeycomb above the braze line - Section II.

      NOTE

      The definitions that follow apply to this inspection.

      1. Definitions.

         1. DEFORMED CELLS: Cells which have incomplete or damaged walls. Includes cracked, torn, split, separated, missing, or crushed cell walls.

         2. FOREIGN OBJECT DAMAGE (FOD): Damage to an engine, module, assembly, component, or engine part by an external object which causes the part to become unserviceable and not to engineering or quality standards.

         3. LOOSE MATERIAL: Any material that is not firmly attached (the material can be moved with a probe).

         4. SEPARATED WALL: A separation between walls which permits light to pass through.

         5. SPLIT CELL WALL: A fracture in the cell wall. See Figure.

         6. LAYOVER/BURRS: Metal which is laid over during processing and does not interfere with the measurement of the cell height.

         7. REDEPOSITED REMELT: Displacement of metal caused by the EDMR process. See Figure.

      2. Deformed cells, separated walls, and split cell walls.

         1. Incomplete cells due to processing (machining cutoff) or those affected by chamfers must be ignored.

         2. For honeycomb that has a total width of five staggered rows or less, the maximum number of cells is two for each linear inch (25.4 mm) with a maximum size not to extend across the full width. See Figure.

         3. For honeycomb that has a total width greater than five staggered rows, see the applicable step that follows:

            1. Where the total honeycomb area is at least 4 square inches (25.8 square centimeters), see Step.

            2. Where the total honeycomb area is less than 4 square inches (25.8 square centimeters), see Step to calculate (prorate) the maximum number of permitted incomplete cells for each part.

      3. Layover/burrs.

         1. Layover/burrs must not exceed 0.010 inch (0.254 mm), which includes ribbon thickness for both machined surfaces and surfaces that are not machined. See Fig. 70-31-07-990-016.

         2. Loose material is not permitted.

      4. Loose material inside cells.

         1. Loose material inside cells is not permitted.

      5. Cleanliness of cells.

         1. Loose or unwanted material inside cells is not permitted.

   6. Additional requirements for honeycomb machined by spark erosion grinding (EDM).

      1. Special Requirements.

         1. After spark erosion grinding, it is necessary to clean cells by a method that will fully remove oxides and loosely attached remelt deposits that are a result of the grinding process. See Step (2) for the inspection for the presence of oxides.

         2. Sufficient lighting and magnification, up to 30X for 0.062 inch (1.575 mm) or larger cell diameters and 30X or greater for cell diameters less than 0.062 inch (1.575 mm), must be used so that cell sides and bottoms can be clearly seen.

      2. Inspection.

         1. Examine all cells within an approximate 1 inch (25.4 mm) area at approximately eight equal places around the circumference of the honeycomb.

      3. Acceptance limits.

         1. A maximum of two cells at any of the inspection locations can show the presence of oxides on the cell bottoms or side walls. If more than two cells show the presence of oxides, do the cleaning process again. For typical examples of clean cells and cells that have oxides, see Figure and Figure.

         2. Heat discoloration as a result of heat treatment is permitted.

10. SUBTASK 70-31-07-310-010 Deburring of Honeycomb After Grinding to Size

    NOTE

    1. Use clean gloves when you touch the part to prevent injury from sharp edges.

    2. If wet grinding was done, clean by the SPM TASK 70-11-03-300-503; then, dry the part.

    3. If dry grinding was done, blow out any remaining material before blasting.

    1. After final grinding, deburr the honeycomb by one or more of the methods that follow:

       1. Wire brush the honeycomb surface by the installation of a wire brush in the spindle of a machine used for grinding and permit the wire wheel to freewheel touch the honeycomb to deburr. Wire brushing can be done while grinding on a two-spindle machine. Clean by the SPM TASK 70-11-03-300-503.

       2. Wet abrasive blast. Refer to the SPM TASK 70-12-08-300-503. Use a power spray to flush the part with water to remove the blasting slurry; then, dry the part.

       3. Dry abrasive blast. Refer to the SPM TASK 70-12-11-300-503.

       4. Dry plastic blast. Refer to the SPM TASK 70-12-07-120-501.

          1. Use the smallest size plastic grit to blow out any remaining grit.

          2. If plastic grit is caught in the cells (usually 1/32 cell), remove the plastic blast material as follows:

             1. Load parts into an oven with the honeycomb side down.

             2. Bake at 900 deg F (482 deg C) for one hour.

       5. Dry abrasive blast. Refer to the SPM TASK 70-12-09-120-501. Blow out any remaining grit.

11. SUBTASK 70-31-07-310-011 Nickel Plating Thickness

    Alloy	Vacuum	Argon and/or Hydrogen
    Precipitation Hardened Iron Base Alloys	Optional (0.0006 inch max.) (0.015 mm max.)	0.0004 - 0.0006 inch (0.010 - 0.015 mm)
    Precipitation Hardened Nickel Base Alloys (Minimum Ti + Al content less than 4%)	Optional (0.0006 inch max.) (0.015 mm max.)	0.0004 - 0.0006 inch (0.010 - 0.015 mm)
    Precipitation Hardened Nickel Base Alloys (Minimum Ti + Al content 4% or greater)	Optional (0.0006 inch max.) (0.015 mm max.)	0.0008 - 0.0012 inch (0.020 - 0.030 mm)
    All other alloys	Optional (0.0006 inch max.) (0.015 mm max.)	Optional (0.0006 inch max.) (0.015 mm max.)
    Nickel plating in areas other than joints is optional and is not always complete.

12. SUBTASK 70-31-07-310-012 Filler Metal

    Identification	Braze Filler Metal
    Process 1	CoMat 03-178 BRAZING ALLOY, NICKELBASE CoMat 03-151 HIGH TEMP. BRAZING FILLERPOWDER CoMat 03-154 BRAZING FILLER POWDER
    Process 2	CoMat 03-249 BRAZING FILLER MATERIAL,Ni-BASE
    Process 3	CoMat 03-163 HIGH TEMP. BRAZING FILLERPOWDER CoMat 03-164 HIGH TEMP. BRAZING FILLERPOWDER CoMat 03-179 BRAZING FILLER METAL,NICKEL BASE
    Process 4	CoMat 03-114 BRAZE FILLER METAL 82Au-18Ni CoMat 03-115 BRAZE FILLER METAL 82Au-18Ni CoMat 03-116 BRAZE FILLER METAL 82Au-18Ni
    Process 5	CoMat 03-176 BRAZING FILLER METAL
    If no identification is given, use Process 1.

13. SUBTASK 70-31-07-310-013 Brazing Atmosphere

    Type	Dew Point Maximum (See Note 1)	Pressure/Purity	Application
    Vacuum	-	5x10-4 torr (0.5 micron Hg) or better. (See Notes 2 and 3)	Furnace Brazing
    Argon	-35 deg F (-37 deg C) or Better.	99.99 percent minimum	Induction or Furnace Brazing and Vacuum Furnace Back-Fill
    Hydrogen	-35 deg F (-37 deg C) or Better.	99.94 percent minimum	Furnace Brazing
    Argon + Hydrogen (see Note 4)	(See Note 5)	(See Note 5)	Furnace Brazing
    Notes:
    1. When possible, use the brazing chamber exhaust gas to calculate the dew point.
    2. The maximum leak rate is 60 microns Hg/hr measured at room temperature after pumping down to 1 micron Hg or at a lower pressure and blocking pumps.
    3. Partial pressure of argon is permitted if you back-fill with argon after you have the necessary vacuum.
    4. The mixture can be in any proportion.
    5. The purity or dew point of argon and hydrogen in the mixture must be as shown above.

14. SUBTASK 70-31-07-310-014 Brazing Temperature

    Identification	Stabilized Temperature and Pressure	Brazing Temperature Maximum (See Note)
    Process 1	1675 - 1750 deg F (913 - 954 deg C)	1975 deg F (1079 deg C)
    Process 2	1675 - 1750 deg F (913 - 954 deg C)	1950 deg F (1066 deg C)
    Process 3	1875 - 1925 deg F (1024 - 1052 deg C)	2175 deg F (1191 deg C)
    Process 4	1400 - 1650 deg F (760 - 899 deg C)	1850 deg F (1010 deg C)
    Process 5	1400 - 1450 deg F (760 - 788 deg C)	1850 deg F (1010 deg C)
    The part temperature must not be more than the maximum temperature during the brazing cycle.

15. SUBTASK 70-31-07-310-015 Limits for Unbonded Cells in Full Ring Assemblies

    1. Limits for unbonded peripheral cells:

       Cell Size	Maximum number of unbonded cells in any 5 Inches (127 mm) of peripheral length
       0.031 inch (0.787 mm)	20
       0.062 inch (1.575 mm)	10
       0.125 inch (3.175 mm)	5

    2. Limits for unbonded center cells:

       Cell Size	Maximum number of unbonded cells in any 2 Square Inch (12.9 sq.cm) Area
       0.031 inch (0.787 mm )	270
       0.062 inch (1.575 mm)	70
       0.125 inch (3.175 mm)	18

16. SUBTASK 70-31-07-310-016 Limits for Unbonded Peripheral Cells in Segmented Assemblies

    1. Segments with 5 inch (127 mm) or more peripheral length:

       Cell Size	Maximum number of unbonded cells in any 5 inches (127 mm) of peripheral length
       0.031 inch (0.787 mm)	20
       0.062 inch (1.575 mm)	10
       0.125 inch (3.175 mm)	5

    2. Segments with less than 5 inch (127 mm) peripheral length:

       Cell Size	Maximum number of unbonded cells/inch (25.4 mm) of peripheral length
       0.031 inch (0.787 mm)	4 (See Note)
       0.062 inch (1.575 mm)	2 (See Note)
       Non-metric example: If a part has 0.062 inch cells and the periperal length is calculated to be 4.5 inches, the total number of unbonded cells/part is 9 (4.5x2).
       Metric example: If a part has 1.575 mm cells and the periperal length is calculated to be 114.3 mm, the total number of unbonded cells/part is 9 (2x114.3/25.47).

17. SUBTASK 70-31-07-310-017 Limits for Unbonded Center Cells in Segmented Assemblies

    1. Limits for segments 2 square inches (12.9 sq. cm) or more in area:

       Cell Size	Maximum number of unbonded cells in any 2 square inch (12.9 sq. cm) area
       0.031 inch (0.787 mm)	270
       0.062 inch (1.575 mm)	70
       0.125 inch (3.175 mm)	18

    2. Limits for segments less than 2 square inches (12.9 sq. cm) in area:

       Cell Size	Maximum number of unbonded cells in any 1 sq. in. (6.45 sq. cm) area
       0.031 inch (0.787 mm)	135 (See Note)
       0.062 inch (1.575 mm)	35 (See Note)
       0.125 inch (3.175 mm)	9 (See Note)
       Non-metric example: If a part has 0.062 inch cells and 1.5 square inches of center area, the total number of unbonded cells/part is 52 (1.5 x 35).
       Metric example: If a part has 1.575 mm cells and 9.675 square centimeters of center area, the total number of unbonded cells/part is 52 (35 x 9.675/6.45).

18. SUBTASK 70-31-07-310-018 Limits for filled cells

    1. Limits for parts 4 square inches (25.8 sq. cm) or more in area:

       Cell Size	Maximum number of filled in any 4 square inch (25.8 sq. cm) area
       0.031 inch (0.787 mm)	200
       0.062 inch (1.575 mm)	52
       0.125 inch (3.175 mm)	12

    2. Limits for parts less than 4 square inches (25.8 sq. cm) in area:

       Cell Size	Maximum number of filled cells in any 1 sq. in. (6.45 sq. cm) area.
       0.031 inch (0.787 mm)	50 (See Note)
       0.062 inch (1.575 mm)	13 (See Note)
       0.125 inch (3.175 mm)	3 (See Note)
       Non-metric example: If a part has 0.062 inch cells and 2.5 square inches of area, the total number of filled cells/part is 32 (2.5 x 13).
       Metric example: If a part has 1.575 mm cells and 16.125 square centimeters of area, the total number of filled cells/part is 32 (13 x 16.125/6.45).

19. SUBTASK 70-31-07-310-019 Limits for Deformed Cells, Separated Walls for parts with a Total Honeycomb Width greater than five staggered rows.

    1. Limits for parts 4 square inches (25.8 sq.cm) or more in area:

       Cell Size	Maximum Number in Any 4 Square Inch (25.8 sq. cm) Area
       0.031 inch (0.787 mm)	80
       0.062 inch (1.575 mm)	20
       0.125 inch (3.175 mm)	8

    2. Limits for parts less than 4 square inches (25.8 sq. cm) in area:

       Cell Size	Maximum Number of Filled Cells in Any 1 sq. in. (6.45 sq. cm) Area.
       0.031 inch (0.787 mm)	20 (See Note)
       0.062 inch (1.575 mm)	5 (See Note)
       0.125 inch (3.175 mm)	2 (See Note)
       Non-metric example: If a part has 0.062 inch cells and 2.5 square inches of area, the total number of incomplete cells/part is 12 (2.5 x 5).
       Metric example: If a part has 1.575 mm cells and 16.125 square centimeters of center area, the total number of incomplete cells/part is 12 (5 x 16.125/6.45).

Figure: Nickel plating Fig. 70-31-07-990-001

Nickel plating Fig. 70-31-07-990-001



Figure: Filler metal Fig. 70-31-07-990-002

Filler metal Fig. 70-31-07-990-002



Figure: Brazing atmosphere Fig. 70-31-07-990-003

Brazing atmosphere Fig. 70-31-07-990-003



Figure: Brazing temperatures Fig. 70-31-07-990-004

Brazing temperatures Fig. 70-31-07-990-004



Figure: Microstructural analysis of too much braze on honeycomb parts

Microstructural analysis of too much braze on honeycomb parts



Figure: Inspection pattern for light probe inspection of vanes (only) as an alternative to the gravity leak test

Inspection pattern for light probe inspection of vanes (only) as an alternative to the gravity leak test



Figure: Peripheral and center cells

Peripheral and center cells



Figure: Peripheral cell with braze line hole

Peripheral cell with braze line hole



Figure: Determination of peripheral length for segments up to five staggered rows wide

Determination of peripheral length for segments up to five staggered rows wide



Figure: Determination of peripheral length for segments greater than five staggered rows wide

Determination of peripheral length for segments greater than five staggered rows wide



Figure: Inspection limits for center cells of segmented parts

Inspection limits for center cells of segmented parts



Figure: Example of a cell wall hole above the braze line

Example of a cell wall hole above the braze line



Figure: Example of a cell wall fracture

Example of a cell wall fracture



Figure: Typical redeposit remelt

Typical redeposit remelt



Figure: Typical redeposit remelt

Typical redeposit remelt



Figure: After braze inspection of honeycomb up to 5 staggered rows wide

After braze inspection of honeycomb up to 5 staggered rows wide



Figure: After braze inspection of honeycomb for layover/burrs

After braze inspection of honeycomb for layover/burrs



Figure: Typical example of clean cells with shiny bottoms

Typical example of clean cells with shiny bottoms



Figure: Typical example of cells with oxides on cell bottoms

Typical example of cells with oxides on cell bottoms