Preliminary Requirements

Safety Requirements

WARNING

IT IS THE RESPONSIBILITY OF THE OPERATOR TO OBTAIN AND OBSERVE THE MANUFACTURER'S MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIALS, AND ALSO TO TAKE LOCAL REGULATION INTO CONSIDERATION. THE SAFETY DATA SHEETS CONTAIN 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.

Procedure

1. SUBTASK 70-34-18-380-001 Prepare the Surface of the Parts for Plasma and Other Thermal Spray Coatings

   1. NOTE

      Other thermal spray coatings include those by gaseous fuel and oxygen, detonation, and dual wire electric arc spray.

      NOTE

      Life-limited disks, hubs, blades, rotor shafts, rotor spacers, drum rotors or knife-edge seals, brush seals, seal plates, and bearing seal faces must be held in a fixture, and mechanized equipment must be used in such a manner that the gun-to-work distance and spray angle stay fixed during blast preparation. Mechanized or manual equipment can be used to prepare all other parts.

      NOTE

      Engine life-limited parts are those specified in Chapter 5 of Engine Manuals and Overhaul Manuals (refer to TASK 05-10-01-200-001-A00 thru -D00) and those other high energy rotating parts such as, disks, spacers, hubs and shafts which have life limits in sections other than Chapter 5 in older overhaul manuals.

      NOTE

      This task is not always applicable to IAE Repair Source-Qualified grit blasting processes. Repair Source-Qualified grit blasting procedures must be approved by the applicable IAE control department.

      Mask the parts.

      1. NOTE

         It may be necessary to touch up the masking after blasting.

         In general, it is usual to mask a part in preparation for shotpeening, if necessary, and before grit blasting in preparation for plasma coating. This reduces the time lag between blasting and the application of the coating and also reduces the possibility of contamination of cleaned and blasted surfaces when they are touched during the procedure to mask them.

      2. The subsequent masking tapes will protect areas from grit blasting, but might not be satisfactory for some thermal spray. Use as necessary. Refer to Step for a fuller description of each tape.

         1. CoMat 02-001 ADHESIVE TAPE (MASKING).

         2. CoMat 02-006 ADHESIVE TAPE ALUMINIUM FOIL

         3. CoMat 02-047 TAPE, HEAT REFLECTIVE.

         4. CoMat 02-050 HIGH TEMPERATURE GLASS CLOTH TAPE.

         5. CoMat 02-198 ADHESIVE TAPE (MASKING METAL SPRAY)

         6. CoMat 02-265 TAPE, DOUBLE LAYER.

         7. CoMat 02-266 TAPE, DOUBLE LAYER.

         8. CoMat 02-267 HEAT RESISTANT TAPE.

         9. CoMat 02-368 TAPE - SILICONE COATED, GLASS FABRIC.

         10. CoMat 02-369A MASKING TAPE (HEAVY)

         11. CoMat 02-372 TAPE - HIGH TEMPERATURE, GLASS CLOTH, COATED.

         12. CoMat 02-373 FABRIC, SILICONE-COATED FIBERGLASS.

         13. CoMat 02-374 TAPE, HEAT-REFLECTIVE.

         14. CoMat 02-375 TAPE-GLASS CLOTH, DOUBLE ADHESIVE, 0.007" THICK.

         15. CoMat 02-376 TAPE-GLASS CLOTH, DOUBLE ADHESIVE, 0.105" THICK.

         16. CoMat 02-377 TAPE-ALUMINUM FOIL, HEAVY DUTY.

         17. CoMat 02-397 TAPE, SILICONE RUBBER/GLASS CLOTH.

         18. CoMat 02-399 TAPE, GLASS FABRIC, SILICONE COATED (BLUE).

      3. You can use CoMat 03-461 MASKANT, PLASMA SPRAY, which is a liquid plasma spray maskant, to prevent the bonding of plasma spray particles. This product is approved as a maskant on parts made of steel, stainless steel, nickel base alloys, cobalt base alloys, aluminum, titanium and titanium alloys.

      4. Sheet metal, Teflon, silicone rubber or other applicable materials can also be used for masking or for locally made masking templates.

   2. Prepare the surface.

      1. Clean the part.

         1. The strength of the plasma coating bond is related to the preparation of the surface and how clean the prepared surface was. Thus, the surfaces of parts must be fully cleaned to remove unwanted materials. A recommended cleaning procedure is degreasing as given in the SPM TASK 70-11-03-300-503.

   3. NOTE

      Masking used during shotpeening must not cause a sharp line of demarcation.

      Mask the part as necessary.

      1. NOTE

         Shotpeening outside the repair area is optional and full coverage is not necessary. The peened areas must not contain any rolled edges or lines of demarcation. Shotpeening is not permitted on knife edges, threads, splines, or surfaces whose finish can be harmed by the peening process.

         Shotpeen life-limited rotating parts.

         1. Life-limited parts which turn (rotate) must have the area to be coated shotpeened to an intensity of 6A unless specified differently. Refer to the SPM TASK 70-38-13-380-501. Use a masking tape given in Step to protect areas from grit blast and prevent overspray on repaired areas.

      2. 
         CAUTION
         THE GRIT BLASTING THAT FOLLOWS SHOULD NOT BE USED TO REMOVE PLASMA SPRAY AND OTHER THERMAL SPRAY COATINGS BECAUSE THIS CAN CAUSE TOO MUCH STOCK LOSS AND MEDIA CONTAMINATION.

         Grit blast the parts.

         All surfaces to be coated must be grit blasted.

         1. Grit type and size.

            1. For titanium parts: Use CoMat 05-192 ALUMINUM OXIDE GRIT or CoMat 05-046 ALUMINUM OXIDE GRIT (No. 60) or finer.

            2. For non-titanium parts: Use CoMat 05-192 ALUMINUM OXIDE GRIT or CoMat 05-046 ALUMINUM OXIDE GRIT (No. 60).

         2. 

            CAUTION

            NINETY DEGREE BLAST ANGLES CAN CAUSE EXCESSIVE BOND LINE CONTAMINATION.

            Angle of blast: 45 degrees to 75 degrees.

         3. Nozzle-to-part distance: 4 in. to 6 in. (102 mm to 152 mm).

         4. Nozzle internal diameter size: 0.25 in. (6.35 mm) thru 0.5 in. (12.7 mm).

         5. Blasting pressures.

            1. For titanium parts:

            2. Pressure-type machine: 20 psi to 30 psi (138 kPa to 207 kPa).

            3. Suction-type machine: 40 psi to 60 psi (276 kPa to 414 kPa).

            4. For non-titanium parts:

            5. Pressure-type machine: 20 psi to 40 psi (138 kPa to 276 kPa).

            6. Suction-type machine: 40 psi to 80 psi (276 kPa to 552 kPa).

   4. Do a check for grit deterioration.

      1. Frequently examine the condition of the grit.

         1. For this inspection, it is necessary to do a check for the percent of fines present and the degree or amount of rounding or polishing of each grain because these affect the quality of the surface produced by the blast.

         2. The blasted part must have a constant dull (matte) texture on all grit blasted surfaces with no shiny (unblasted) areas.

         3. If optional coating areas are to be coated, then prepare these surfaces with the same care as those that are not optional.

   5. Protect the parts.

      1. Do not touch grit blasted surfaces. If you need to touch grit blasted surfaces, wear clean white gloves.

      2. During the time between grit blasting and coating, parts must be covered or put in to containers to give protection to the blasted surfaces from contamination by atmospheric vapors, airborne dirt, and handling. Blow off loose remaining grit with CoMat 03-010 ARGON GAS or dry filtered oil-free air.

      3. If there is contamination of the grit blasted surface with dust, fingerprints or oil, solvent wipe the part if you must touch the part. Refer to the SPM TASK 70-11-26-300-503.

      4. Touch up or replace tape, as necessary; then solvent wipe any areas that you touched. Refer to the SPM TASK 70-11-26-300-503.

   6. NOTE

      If the time between grit blasting and coating the part is more than two hours, it will be necessary to get instructions or approval from your engineering department. It is recommended (to help stay in this limit) that the traveler that goes with the part have space available to record the date and time the part was grit blasted.

      Plasma coat parts as soon as possible after grit blasting (within two hours is recommended).

   7. Remove maskants. If there is any remaining tape, solvent wipe the area. Refer to the SPM TASK 70-11-26-300-503.

2. SUBTASK 70-34-18-160-001 Table of Masking Tapes to Use in Surface Preparation

   Item Number		Description
   CoMat 02-001 ADHESIVE TAPE (MASKING)		Cotton cloth tape, mostly used for grit blasting.
   CoMat 02-006 ADHESIVE TAPE ALUMINIUM FOIL		Aluminum foil tape; mostly used for grit blasting and low heat areas.
   CoMat 02-047 TAPE, HEAT REFLECTIVE		Aluminum foil tape; mostly used for grit blasting and low heat areas.
   CoMat 02-050 HIGH TEMPERATURE GLASS CLOTH TAPE		Fiberglass tape; mostly used to protect areas that are not near heat.
   CoMat 02-198 ADHESIVE TAPE (MASKING METAL SPRAY)		Silicone-coated, glass fabric tape for protection from grit blast operations and thermal spray operations.
   CoMat 02-266 TAPE, DOUBLE LAYER		Silicone layer over aluminum, mostly used for high heat areas and areas with too much plasma build-up.
   CoMat 02-267 HEAT RESISTANT TAPE, CoMat 02-268 HEAT TREATMENT TAPE, CoMat 02-269 HEAT RESISTANT TAPE - DELETED (USE CoMat 02-267)		Silicone tape; mostly used for high heat areas.
   CoMat 02-368 TAPE - SILICONE COATED, GLASS FABRIC		Silicone-coated, glass fabric tape.
   CoMat 02-372 TAPE - HIGH TEMPERATURE, GLASS CLOTH, COATED		High temperature, glass cloth, coated tape used to protect parts during grit blasting and plasma spray operations.
   CoMat 02-373 FABRIC, SILICONE-COATED FIBERGLASS		Silicone-coated fiberglass fabric that protects parts during grit blasting and various thermal spray operations.
   CoMat 02-374 TAPE, HEAT-REFLECTIVE		Aluminum foil, inert glass cloth tape with pressure-sensitive silicone adhesive used as a protective mask in high-temperature processes.
   CoMat 02-375 TAPE-GLASS CLOTH, DOUBLE ADHESIVE, 0.007" THICK, CoMat 02-376 TAPE-GLASS CLOTH, DOUBLE ADHESIVE, 0.105" THICK		Glass cloth tape coated with a pressure-sensitive silicone adhesive on both sides and used as a protective mask in high-temperature processes.
   CoMat 02-377 TAPE-ALUMINUM FOIL, HEAVY DUTY		Aluminum foil tape with pressure-sensitive silicone adhesive used as a protective mask in high-temperature processes.
   CoMat 02-399 TAPE, GLASS FABRIC, SILICONE COATED (BLUE)		Silicone-coated, glass fabric (Blue) tape for protection from grit blast operations and thermal spray operations. Not for use on steel parts.