Preliminary Requirements

Safety Requirements

WARNING

REFER TO THE MANUFACTURER'S MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIAL'S INFORMATION SUCH AS: HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE, EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES.

WARNING

COMAT 02-183 ALUMINIDE COATING CONTAIN FINELY DIVIDED ALUMINUM METAL PARTICLES WHICH CAN INTRODUCE AN EXPLOSIVE HAZARD IF A "DUST CLOUD" OF DRY PARTICLES IS FORMED.

WARNING

COMAT 02-183 ALUMINIDE COATING CONTAINS FINELY DIVIDED COBALT METAL PARTICLES WHICH CAN INTRODUCE AN EXPLOSIVE HAZARD IF A "DUST CLOUD" OF DRY PARTICLES IS FORMED.

CAUTION

SERVICE EXPERIENCE HAS SHOWN THAT CRACKS CAN OCCUR IN TOUCH-UP COATED AREAS OF AIRFOILS AS A RESULT OF INCORRECT COATING APPLICATION.

Procedure

1. SUBTASK 70-38-26-800-001 Limits Of CoMat 02-183 On Turbine Hardware

   1. Unless specified differently in a repair, these limits apply to the turbine hardware that follows.

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

         1. A maximum of three areas/airfoil (1 sq in. (6.45 sq cm) combined with no one area greater than 0.5 sq in. (3.22 sq cm)) can be repaired with this procedure.

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

      2. Blades that exceed the limits that follow must have a total replacement of coating.

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

         2. A maximum of three areas/airfoil (0.5 sq in. (3.22 sq cm) combined) can be repaired by this procedure on the remaining gas path surfaces.

      3. Turbine Airfoil Surface.

         1. Do not use CoMat 02-183 ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY to overcoat an entire turbine airfoil.

      4. Ceramic Coated Areas.

         1. CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY 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. Use masking tape where necessary to keep the CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY away from ceramic coating on the part. CoMat 02-183B TAPE, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY must not be applied to or be permitted to touch, any ceramic coated area of the part because the aluminide coating is harmful to the ceramic bond.

2. SUBTASK 70-38-26-380-001 Prepare the Materials

   1. Prepare the CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY.

      1. 
         WARNING
         CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY RESIDUE CAN REACT WITH ALKALIES OR ACID AND GIVE OFF HYDROGEN GAS, WHICH CAN EXPLODE.

         Before use, stir or shake the slurry in the initial container or use a roller mixer to mix the slurry in the initial container, to suspend the powder and break up agglomerates, until all solids are equally dispersed. It is recommended to agitate the slurry during use to keep the powder in suspension.

         1. Be sure to keep the slurry tightly sealed in the initial container in a cool location when it is not in use. The shelf life is limited to 24 months from the date of manufacture. Be sure to check the expiration date on the container before use.

3. SUBTASK 70-38-26-380-002 Prepare the Surfaces to be Painted

   1. 

      CAUTION

      IF NOT CORRECTLY MASKED, COATED SURFACES ADJACENT TO THE AREA TO BE TOUCHED UP COULD BE DAMAGED BY GRIT BLAST; THE RESULT IS A REDUCTION IN COATING PROTECTION.

      Apply masking tape to ceramic coated areas.

   2. Grit blast the area to be coated with to remove the thin heat tint oxide layer and to get a matte surface. Use SPOP 218 at 20 psi (137.9 kPa) in a pressure-type cabinet or at 30 psi (206.8 kPa) in a suction-type cabinet and a standoff distance of 3.0 in. - 5.0 in. (76 mm - 127 mm). Refer to SPM TASK 70-12-09-120-501.

   3. Remove masking.

   4. Blow remaining abrasive grit off the part with clean, filtered air at 30 psi (206.8 kPa) maximum. Be sure to remove all blasting grit and any remaining masking tape.

   5. 

      CAUTION

      CLEAN GLOVES MUST BE WORN WHEN YOU TOUCH SURFACES AFTER CLEANING AND BEFORE APPLICATION OF TOUCH-UP COAT TO PREVENT CONTAMINATION THAT CAN CAUSE AN UNSATISFACTORY COATING-TO-SURFACE BOND.

      Clean all surfaces by the solvent wipe method and air dry. Refer to SPM TASK 70-11-26-300-503.

   6. 

      CAUTION

      IF CoMat 02-183 ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY IS IN CONTACT WITH CERAMIC COATING DURING THE DIFFUSION HEAT TREATMENT, DAMAGE TO THE BOND BETWEEN THE PART AND THE CERAMIC COATING WILL OCCUR.

      If the repair area is adjacent to areas that have ceramic coating, apply masking where necessary to keep the CoMat 02-183 ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY away from the ceramic coating.

4. SUBTASK 70-38-26-380-003 Apply the Surface Coating

   1. 
      CAUTION
      DO NOT EXCEED ONE HOUR BETWEEN SURFACE PREPARATION AND COATING APPLICATION. A DELAY IN COATING APPLICATION CAN CAUSE CONTAMINATION OF THE SURFACES TO BE COATED.

      Application of CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY.

      1. 
         WARNING
         CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY RESIDUE CAN REACT WITH ALKALIES OR ACID AND GIVE OFF HYDROGEN GAS, WHICH CAN EXPLODE.
         
         WARNING
         IF A WATERFALL-TYPE SPRAY BOOTH IS USED, KEEP WATER NEUTRAL TO MINIMIZE THE POSSIBILITY OF HYDROGEN GAS FORMATION.
         
         WARNING
         ACCUMULATIONS OF ANY REMAINING PAINT IN SPRAY BOOTH EXHAUST DUCTS AND EQUIPMENT CAN INTRODUCE AN EXPLOSIVE HAZARD.

         Do the subsequent procedure to apply the CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY.

         1. Use a brush to apply a thin uniform wet coat of CoMat 02-183A SLURRY, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY directly onto the grit blasted area of the part to be touched up and onto the test sample(s).

            NOTE

            It is the responsibility of the local quality assurance organization to calculate the necessary number of test samples for each lot/batch of parts.

            1. During this procedure, continue to stir or shake the slurry or to mix the slurry on a roller mixer, to be sure the solids do not settle out.

            2. Apply the slurry as equally as possible.

            3. Overlap with old coating must be continuous and evenly faired, but should not exceed the dimensions given in surface preparation.

         2. Cure in an electric oven at 275 deg F - 325 deg F (155 deg C - 163 deg C) for not less than 15 minutes.

         3. Air cool to room temperature.

      2. Measure the thickness of the cured PWA 545-1 slurry on the test sample(s). The necessary thickness is to make sure that the touch-up areas will have a full layer of diffused coating after the diffusion heat treatment is 0.010 in. - 0.015 in. (0.254 mm - 0.381 mm). To get this result, do the application, cure, cool and measure steps above, as necessary. Two or three coats of slurry is typical.

         1. If slurry amount is within limits, go to the masking removal step below.

         2. If slurry amount is below limits, do the application, cure, cool and weigh measure steps above again.

         3. If slurry amount is greater than the limits, scrub off cured slurry with a stiff brush and water and do the entire procedure again; start with surface preparation procedure.

      3. 
         CAUTION
         DO NOT TOUCH COATED SURFACES UNTIL AFTER DIFFUSION HEAT TREATMENT TO PREVENT DAMAGE TO COATING. (REFER TO THE DIFFUSION HEAT TREATMENT PROCEDURE).

         Remove the masking tape and examine cured slurry coating for cracks or spalling.

         1. If the cured slurry coating shows cracks or spalling, scrub off the cured slurry with a stiff non-metallic brush and water. Do the surface preparation procedure above again and then do the above steps in this apply the touch-up coating procedure again.

      4. Diffusion heat treatment must be done as soon as possible after application, but not later than eight hours after application.

   2. CoMat 02-183B TAPE, ALUMINIDE COATING - LOCALIZED APPLICATION, LOW ACTIVITY.

      1. Apply PWA 545-2 coating tape directly onto the grit blasted area of the part to be touched up. Apply the number of layers specified in the repair.

         NOTE

         The use of an adhesive backing will help hold the tape in position before diffusion heat treatment.

      2. Make sure that the tape stays in direct contact with the part during the total length of the diffusion heat treat cycle.

         NOTE

         Air pockets or separation between the tape and the part will prevent coating deposition.

         NOTE

         The adhesive burns off at a very low temperature and will not hold the tape in position after burn-off.

      3. Diffusion heat treatment must be done as soon as possible after application, but not later than eight hours after application.

5. SUBTASK 70-38-26-370-001 Diffusion Heat Treatment

   1. Put the parts very carefully in a rack. Put the rack into a furnace. Make sure you do not cause damage to the surface coatings.

   2. Increase the temperature of the parts, in a hydrogen or argon gas furnace to 1950 deg F to 2000 deg F (1066 deg C to 1094 deg C). Keep the parts at this temperature for four hours.

   3. Reduce the temperature of the parts to 1600 deg F (871 deg C) in a controlled atmosphere. Reduce the temperature at a rate equal to an air cool of 35 deg F (19.4 deg C) for each minute (or faster). When the parts are at 1600 deg F (871 deg C), remove the parts from the oven. Let the parts become cool.

   4. Clean off undiffused powdery residue and oxide film.

      1. Scrubbing with a stiff brush and water and then drying with shop air.

      2. Dry abrasive blast with SPOP 218, but use one of the specified No. 240 aluminum oxide grits, a pressure of approximately 20 psi (137.9 kPa) in a pressure-type cabinet or at 30 psi (206.8 kPa) in a suction-type cabinet and a standoff distance of 3.0 in. - 5.0 in. (76 mm - 127 mm).

   5. Do an inspection of the part to make sure that there is a full layer of coating on the touch-up areas.