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. THESE CONTAIN 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.

WARNING

CoMat 07-057 SLURRY, ALUMINIUM-SILICON AND CoMat 07-176 COATING TAPE CONTAIN FINELY DIVIDED ALUMINUM METAL. SMALL SIZED PARTICLES OF ALUMINUM POWDER CAN BE AN EXPLOSION HAZARD. DO NOT LET DRY ALUMINUM PARTICLES FORM A "DUST CLOUD".

CAUTION

INCORRECT APPLICATION OF THE TOUCH-UP COATING CAN CAUSE CRACKS TO OCCUR IN THE TOUCH-UP COATED AREAS OF AIRFOILS.

CAUTION

WHEN THE SPM TASK 70-38-26-380-501 IS SPECIFIED BY THE ENGINE MANUAL, THE SPM TASK 70-38-14-380-501 MUST NOT BE USED AS AN ALTERNATIVE BECAUSE CRACKS CAN OCCUR.

Procedure

1. SUBTASK 70-38-14-380-005 Limits Applicable to CoMat 07-057 Slurry, Aluminum-silicon or CoMat 07-176 Coating Tape on Turbine Hardware

   1. Unless specified differently by the Engine Manual, the subsequent limits apply to the turbine hardware below.

      1. Vanes that exceed the subsequent limits must have a total replacement of coating.

         1. It is permitted to do this procedure to repair a maximum of three areas on each airfoil, and the total repair surface area on each airfoil must be less than or equal to 1 square inch or 6.45 square centimeters, with no one area greater than 0.5 square inch or 3.22 square centimeters.

         2. Leading edge, trailing edge, inner platform to airfoil radius, and outer platform to airfoil radius can be included in any one repair.

      2. When the blade limits are more than what is in the subsequent list, a total replacement of the coating is necessary.

         1. No repairs are permitted on leading edges and it is recommended that there should be no touch-up repairs on trailing edges.

         2. It is permitted to do this procedure to repair a maximum of three areas on each airfoil, and the total repair surface area on each airfoil must be less than or equal to 0.5 square inch or 3.22 square centimeters.

      3. Turbine Airfoil Surfaces

         1. Do not use CoMat 07-057 SLURRY, ALUMINIUM-SILICON or CoMat 07-176 COATING TAPE to overcoat an entire turbine airfoil.

      4. Ceramic Coated Areas

         1. CoMat 07-057 SLURRY, ALUMINIUM-SILICON must not be painted on, or be permitted to touch, any ceramic coated area of the part because the aluminide coating is harmful to the ceramic bond.

         2. CoMat 07-176 COATING TAPE must not be painted on, or be permitted to touch, any ceramic coated area of the part because the aluminide coating is harmful to the ceramic bond.

2. SUBTASK 70-38-14-380-001 Material Preparation

   1. CoMat 07-057 SLURRY, ALUMINIUM-SILICON.

      1. NOTE

         Make sure you keep the slurry tightly sealed in the initial container in a cool place when not in use. Shelf life is unlimited, but the solid particles in the slurry will fall (settle) to the bottom of the container.

         Before use, stir or agitate the aluminum-silicone slurry in the initial container to suspend the powder or break up agglomerates. Stir or agitate until all solids are equally dispersed. It is recommended to stir or shake the slurry during use to keep the powder in suspension.

3. SUBTASK 70-38-14-380-002 Surface Preparation

   1. 

      CAUTION

      TO PREVENT CONTAMINATION WHICH CAN CAUSE THE COATING TO NOT BOND TO SURFACES, MAKE SURE YOU WEAR CLEAN GLOVES WHEN YOU TOUCH SURFACES AFTER YOU HAVE CLEANED THE PART AND BEFORE YOU APPLY THE TOUCH-UP COAT.

      Aqueous degrease the part. Refer to the SPM TASK 70-11-03-300-503.

   2. 

      CAUTION

      WHEN THE COATED SURFACES OF THE TOUCH-UP AREA ARE NOT SATISFACTORILY MASKED THE RESULT WILL BE LESS PROTECTION OF THE COAT WHEN THE GRIT BLAST PROCEDURE IS USED ON THE ADJACENT AREA.

      Apply masking tape from the SPM TASK 70-34-18-380-501, to areas that are not to be coated.

   3. 
      CAUTION
      IF YOU USE THE SPM TASK 70-12-06-120-501 TO GRIT BLAST AIR COOLED AIRFOILS, ABRASIVE COMPOUND CAN CAUSE A BLOCKAGE OF THE COOLING HOLE PASSAGES AND CAN DECREASE THE FLOW OF COOLING AIR THROUGH THESE PASSAGES.

      Use one of the subsequent blast procedures to remove scale and oxides from the area to be painted. Do not use the SPM TASK 70-12-06-120-501 on air-cooled airfoils or on hollow airfoils with blind openings.

      1. The SPM TASK 70-12-09-120-501 Dry abrasive blast with 240/320 grit aluminum oxide.

      2. The SPM TASK 70-12-06-120-501 Wet abrasive blast with 240/320 grit aluminum oxide.

   4. Remove masking.

   5. Rinse clean by power flushing (water blast). Make sure you remove all blasting grit and all remaining masking tape.

   6. Clean all surfaces by the subsequent steps:

      1. Locally swab or wipe clean with solvent by the SPM TASK 70-11-26-300-503.

      2. Air dry.

   7. Apply a mask again to the areas that are not to be coated. Overlap the mask onto the old coat 0.010 to 0.100 inch (0.25 to 2.54 mm.).

4. SUBTASK 70-38-14-380-003 Procedure

   1. 
      WARNING
      CoMat 07-057 SLURRY, ALUMINIUM-SILICON RESIDUE CAN REACT WITH ALKALIES OR ACIDS TO GIVE OFF HYDROGEN GAS, WHICH CAN EXPLODE.
      
      WARNING
      IF A WATERFALL-TYPE SPRAY BOOTH IS USED, IT IS NECESSARY TO KEEP THE WATER NEUTRAL TO MINIMIZE THE PRODUCTION OF HYDROGEN GAS.
      
      WARNING
      SLURRY REMAINING IN THE SPRAY BOOTH, EXHAUST DUCTS AND EQUIPMENT CAN CAUSE AN EXPLOSION CONDITION.
      
      CAUTION
      THE TIME BETWEEN SURFACE PREPARATION AND COATING APPLICATION MUST NOT BE MORE THAN ONE HOUR. A DELAY IN COATING CAN CAUSE CONTAMINATION OF THE SURFACES TO BE COATED.

      Apply CoMat 07-057 SLURRY, ALUMINIUM-SILICON by the subsequent steps:

      1. Equipment.

         1. Brush (recommended).

         2. Spray (permitted).

      2. NOTE

         It is necessary to continue to shake or mix the CoMat 07-057 SLURRY, ALUMINIUM-SILICON when you apply it to make sure solids do not fall to the bottom of the container.

         Apply the first thin wet coat of CoMat 07-057 SLURRY, ALUMINIUM-SILICON equally and directly onto the grit blasted area of the part to be touched up.

      3. Let the coat on the parts and test sample change from green to a gray color.

      4. Cure the CoMat 07-057 SLURRY, ALUMINIUM-SILICON with heat lamps, or in an electric oven at a temperature of 150 to 200 deg F (66 to 93 deg C) for 15 minutes.

      5. Air cool to the ambient temperature.

      6. Do the above steps from CoMat 07-057 SLURRY, ALUMINIUM-SILICON application thru air cool again. Overlap the CoMat 07-057 SLURRY, ALUMINIUM-SILICON onto the coating around the repair area. Refer to the application step in the Step.

      7. Do the above steps from CoMat 07-057 SLURRY, ALUMINIUM-SILICON application thru air cool again. Overlap the CoMat 07-057 SLURRY, ALUMINIUM-SILICON onto the coating around the repair area. Refer to the application step in the Step.

      8. Measure the thickness of the cured CoMat 07-057 SLURRY, ALUMINIUM-SILICON coating (three coats) on the test sample. Use a micrometer or an NDI thickness gage calibrated on an uncoated piece of test sample material.

         1. If the thickness of the coating is 5 to 7 mils in three-coat area, go to the masking removal step below.

         2. If the thickness of the coating is less than 5 mils, repeat the CoMat 07-057 SLURRY, ALUMINIUM-SILICON coating application thru air cool again.

         3. If the thickness of the coating is greater than 7 mils, scrub off the cured CoMat 07-057 SLURRY, ALUMINIUM-SILICON coating with a soft brush and water. Then do this TASK again from Step.

      9. 

         CAUTION

         TO PREVENT DAMAGE TO THE COATING, IT IS NOT PERMITTED TO TOUCH COATED SURFACES UNTIL AFTER THE DIFFUSION HEAT TREATMENT.

         Remove masking tape and examine the cured CoMat 07-057 SLURRY, ALUMINIUM-SILICON coating for cracks or spalling. If there are any such indications, scrub off the cured CoMat 07-057 SLURRY, ALUMINIUM-SILICON coating with water and a soft brush. Then do this TASK again from Step.

      10. NOTE

          The diffusion heat treatment must be done as soon as possible after the CoMat 07-057 SLURRY, ALUMINIUM-SILICON coating is applied but not later than eight hours after application of the CoMat 07-057 SLURRY, ALUMINIUM-SILICON. It is necessary to keep parts in a humidity-controlled area after the CoMat 07-057 SLURRY, ALUMINIUM-SILICON application until after diffusion heat treatment.

          Diffusion heat treat the coating by Step.

   2. Apply CoMat 07-176 COATING TAPE by the subsequent steps:

      1. NOTE

         An adhesive backing helps to hold the tape in place before diffusion heat treatment.

         Apply the CoMat 07-176 COATING TAPE directly onto the grit blasted area of the part to be touched up. Apply the number of layers specified by the engine Manual.

      2. 

         CAUTION

         AIR POCKETS OR SEPARATION BETWEEN THE TAPE AND THE PART CAUSES AN UNSATISFACTORY COATING TO OCCUR.

         NOTE

         The adhesive burns off at a very low temperature. The tape does not stay in place after the adhesive has burnt-off.

         Make sure that the tape continues to touch the part during the full diffusion heat treatment cycle.

      3. NOTE

         The diffusion heat treatment must be done as soon as possible after the CoMat 07-176 COATING TAPE is applied but not later than eight hours after application of the CoMat 07-176 COATING TAPE. It is necessary to keep parts in a humidity-controlled area after the CoMat 07-176 COATING TAPE application until after diffusion heat treatment.

         Diffusion heat treat the coating by Step.

5. SUBTASK 70-38-14-380-004 Diffusion Heat Treatment

   1. To prevent damage to the CoMat 07-057 SLURRY, ALUMINIUM-SILICON, or CoMat 07-176 COATING TAPE coated parts, put the parts very carefully in the heat treatment rack and then put the rack into the furnace.

   2. Heat treat the coated parts in a hydrogen (-40 deg dew point) atmosphere furnace at 1950 to 2000 deg F (1065 to 1094 deg C) for 4 hours. High purity argon (less than -40 deg dew point) can be used as an alternative.

   3. Decrease the temperature of the parts to 1600 deg F (871 deg C) in a protective atmosphere at a rate equivalent to air cooling at 35 deg F (19 deg C)/ minute, or faster. When the temperature is at 1600 deg F (871 deg C), you can remove the parts from the furnace for further air cooling.

   4. Use one of the subsequent procedures to remove (clean off) undiffused powdery residues and oxide film.

      1. Scrub with a stiff brush and water, and then dry with a blast of shop air.

      2. Dry abrasive blast with CoMat 05-022 ALUMINUM OXIDE ABRASIVE at 20 psi (137.9 kPa) in a pressure-type cabinet or at 30 psi (206.8 kPa) in a suction-type cabinet. Use a nozzle-to-part distance of 3.0 to 5.0 inched (76 to 127 mm).

   5. Precipitation heat treat and shot peen specified surfaces as specified in the instructions in applicable Engine Manual.