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.

Procedure

1. SUBTASK 70-28-01-300-001 General

   1. This procedure examines turbine parts for coating on specified areas or for sufficient removal of coating after stripping.

   2. TASK 70-28-01-280-501 does not give an indication of the thickness of a coating. Thus, IAE recommends that you apply a new coating to blades if you subsequently install them in an engine for a long period of time.

   3. Heat tint inspection shows an indication of only a metallic coating.

   4. Heat tint inspection does not show an indication of a thermal barrier (ceramic) coating. Use visual inspection to examine parts for ceramic coating.

   5. In areas where the ceramic coating has damage, it is possible to use the heat tint inspection to do a check for the base metallic coating.

   6. It is important to examine blast gun nozzles frequently for too much wear due to high pressure, and to replace them, when necessary, so that the cleaning process continues to be satisfactory.

   7. If shotpeen is specified by the Engine Manual repair to apply a compressive stress effect to the part, and if the heat tint temperature is higher than 1200 F (648.9 C), then it is necessary to do the heat tint procedure before you do the shotpeen procedure.

   8. Touch parts only with clean white gloves during the procedure to prevent fingerprints on parts.

   9. The IAE 2P16224 (Ref IAE 31383) color photograph for Turbine Blade/Vane inspection shows heat-tinted nickel alloy turbine blades and vanes with IAE 47, IAE 73, IAE 73/IAE 70, IAE 270, IAE 273, IAE 275, IAE 286, IAE 545, IAE 596, IAE 36095, IAE 36330, or IAE 36395 Coating.

2. SUBTASK 70-28-01-110-001 Clean Coated Parts before Heat Tint Procedure

   1. Nickel alloy turbine parts coated with IAE 47, IAE 73, IAE 73/IAE 70, IAE 270, IAE 273, IAE 275, IAE 286, IAE 545, IAE 596, IAE 36095, IAE 36330, or with IAE 36395 plasma spray deposits.

      1. If necessary, remove grease or oil. Refer to the SPM TASK 70-11-03-300-503.

      2. NOTE

         This step is not necessary if parts have been previously cleaned by the SPM TASK 70-11-13-300-503 or chemically stripped.

         NOTE

         Sulfidation can show as a blister or a corrosion pit. For removal of sulfidation, refer to specified section of the engine manual for repair to the part.

         Clean the parts. Refer to the SPM TASK 70-11-13-300-503.

      3. NOTE

         Use a serviceable Otoscope, or equivalent, from any medical supply center, to examine internal cavities and trailing edge openings.

         It is necessary to examine blast gun nozzles frequently for too much wear, caused by high pressure, and to replace them when necessary so that the cleaning procedure continues to be satisfactory.

         Dry abrasive grit blast with the SPM TASK 70-12-11-300-503 or TASK 70-12-09-120-501 to get a smooth matte surface and until all remaining greenish-to-pale blue corrosion is fully removed.

      4. 

         CAUTION

         THE USE OF OVERSIZED MEDIA CAN CAUSE COOLING AIRHOLES TO BECOME CLOGGED.

         Remove remaining abrasive material from the part with a clean, dry airblast free of oil.

      5. 

         CAUTION

         TOUCH PARTS ONLY WITH CLEAN WHITE GLOVES DURING THE PROCEDURE TO PREVENT FINGERPRINTS ON PARTS.

         Move parts directly to heat tint trays.

3. SUBTASK 70-28-01-370-001 Heat Tint

   1. NOTE

      An electric air circulating furnace is recommended. If only a gas furnace is available, protect parts from direct exposure to combustion products of gas-fired burners. Make sure there is sufficient movement of air in the furnace (this increases the heat tint oxide on the part surface).

      Procedure.

      1. Put the part in a circulating air furnace for the applicable amount of time and temperature specified below:

         Part Type	Coating Type	Temperature of Furnace	Time in Minutes
         All Parts	IAE 70	875 deg. F - 925 deg. F (468 deg. C - 496 deg. C)	45-75
         IAE 655 Nickel Alloy	All Types, Except IAE 70	1325 deg. F - 1375 deg. F (718 deg. C - 746 deg. C)	45-75
         IAE 1422 Blades	IAE 273 or IAE 275	1050 deg. F - 1100 deg. F (566 deg. C - 593 deg. C)	45-75
         All Other Parts	All Types, Except IAE 70	1050 deg. F - 1100 deg. F (566 deg. C - 593 deg. C) or 1275 deg. F - 1325 deg. F (691 deg. C - 718 deg. C)	45-75 or 20 - 30

      2. Let temperature of parts decrease in air.

   2. 
      CAUTION
      TOUCH PARTS ONLY WITH CLEAN WHITE GLOVES DURING THE PROCEDURE TO PREVENT FINGERPRINTS ON PARTS.

      NOTE

      A gold or pewter color shows the presence of coat.

      Visual inspection to find presence or absence of coating.

      1. Do this inspection after heat treatment. Keep the parts clean from oil or dust during any delays in the process.

         1. For IAE 655 nickel alloy parts (with any type of coat):

            1. A gold or pewter color is an indication of coating.

            2. A blue or purple color is an indication of no coating.

         2. For parts coated with IAE 70:

            1. A gold or pewter color is an indication of coating.

            2. A blue or purple color is an indication of no coating.

         3. For parts coated with IAE 73/IAE 70:

            1. A gold or pewter color is an indication of IAE 73/IAE 70 coating.

            2. The IAE 70 (only) coat areas show as mottled (spots or streaks) or brownish-blue because of the oxidation of the Cr-rich base metal.

            3. A blue or purple color is an indication of no coating.

         4. For all other parts not included above:

            1. A gold or pewter color is an indication of coating.

            2. A blue or purple color is an indication of no coating.

      2. Compare the color tints with color photograph IAE 2P16224 (Ref PWA 31383) to see if there are any remaining hot corrosion products. (Copies of the photograph can be obtained from IAE Supplier Code IAE00.).

         1. Blade or vane must be equivalent to Blade No. 1 of photograph (See full description in step C.(1).

         2. If blade or vane is equivalent to blade No. 2 or 3, there are remaining hot corrosion products on the part. Do the cleaning procedure in Step again and the heat tint procedure in step 3.A. Refer to the detailed description for blade No. 2 or 3 that shows different amounts of heat corrosion and coating loss.

      3. Parts must be within the specified blend limits, specially when you try to remove hot corrosion products many times.

   3. 
      CAUTION
      ALL PRODUCTS OF HOT CORROSION AND OXIDATION MUST BE REMOVED BEFORE MORE TREATMENT EVEN IF THIS CAUSES A LOSS OF THE PART BECAUSE OF TOO MUCH BLENDING.

      NOTE

      Indicated presence of coating does not indicate actual thickness of the coating. Therefore, IAE recommends that you recoat blades fully if the blade will subsequently be installed in an engine for an extended period of time.

      IAE 2P16224 Turbine blade/vane inspection photograph shows heat-tinted nickel alloy turbine blades and vanes with IAE 47, IAE 73, IAE 73/IAE 70, IAE 270, IAE 273, IAE 275, IAE 286, IAE 545, IAE 596, IAE 36095, IAE 36330, or IAE 36395 coating.

      1. Blade No. 1 is satisfactorily clean.

         1. The dull dark blue color (Arrows A) or purple color on airfoil and root is usual of nickel-base alloys with no coating.

         2. Many shades of gold color (Arrows B, C, and D) are usual of many thicknesses of IAE 47, IAE 73, IAE 73/IAE 73, IAE 270, IAE 273, IAE 275, IAE 286, IAE 545, IAE 596, IAE 36095, IAE 36330, or IAE 36395 coat thinned by abrasive blast.

      2. Blades No. 2 and 3 show different quantities of hot corrosion and IAE 47, IAE 73, IAE 73/IAE 70, IAE 270, IAE 273, IAE 275, IAE 286, IAE 36095, IAE 36330, or IAE 36395 loss.

         1. Badly corroded areas are green (Arrows A) or gray (Arrows B).

         2. Less badly corroded areas are light blue (Arrows C).

         3. Root areas with no coat are dark blue (Arrows D) or purple in contrast to the light blue of the less badly corroded areas (Arrows C) on the airfoil.

         4. A gold color (Arrows E) is an indication of a the presence of coating.

   4. Optional Procedure to Remove Heat Treatment Discoloration of IAE 264 Ceramic Coating.

      1. Different heat treatment atmospheres can cause the color of IAE 264 ceramic coating to change during heat treatment repairs.

         1. Heat treatment in an air atmosphere usually does not cause the color of the ceramic coating to change from the initial white color.

         2. Heat treatment in a hydrogen atmosphere can cause the white color of the ceramic coating to change to gray. The resulting shade of gray is related to the heat treatment temperature.

         3. Heat treatment in a vacuum atmosphere can cause the white color of the ceramic coating to change to gray.

         4. Heat treatment in an argon atmosphere can cause the white color of the ceramic coating to change to gray or blue. The resulting shade of gray or blue is related to the heat treatment temperature.

      2. If the heat treatment discoloration of the IAE 264 ceramic coating is not accepted, do the procedure that follows to whiten the discolored ceramic coating:

         NOTE

         The heat treatment discoloration is cosmetic and does not have an effect of the function or performance of the coating.

         1. Bake the part in an air atmosphere of a circulating air furnace at 1275 deg. F - 1325 deg. F (691 deg. C - 718 deg. C) for 20 - 30 minutes.

         2. Let the temperature of the part decrease in ambient air.