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, PRECUATIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES AND ALSO TO TAKE LOCAL REGULATIONS INTO CONSIDERATION.

WARNING

EVERY POSSIBLE CARE MUST BE TAKEN TO AVOID THE SOLUTION COMING INTO CONTACT WITH THE EYES OR BARE SKIN. PROTECTIVE CLOTHING INCLUDING RUBBER GLOVES AND GOGGLES MUST BE PROVIDED FOR THE OPERATORS WHEN PREPARING AND USING THE NITRIC OR HYDROFLUORIC ACID SOLUTION. RUBBER GLOVES SHOULD BE CHECKED REGULARLY FOR PIN HOLES AND REPLACED IF NECESSARY.

SAFETY NOTICES MUST BE PLACED IN A CONSPICUOUS PLACE.

EYE-WASH BOTTLES AND HF BURN JELLY MUST BE PROVIDED AS CLOSE AS POSSIBLE TO THE PLACE OF WORK.

IF SKIN BECOMES CONTAMINATED WITH THE SOLUTION IT MUST BE RINSED WITH COPIOUS AMOUNTS OF CLEAN RUNNING WATER.

ALL BURNS, HOWEVER SLIGHT, SHOULD BE TREATED AT THE NEAREST SURGERY OR FIRST AID POST.

THE SURGERY MUST BE TOLD WHICH SOLUTION (THE ACIDS INVOLVED) HAS CAUSED THE BURN. THIS APPLIES PARTICULARLY WHEN HYDROFLUORIC ACID IS A CONSTITUENT.

Procedure

1. SUBTASK 70-02-03-220-001 Prepare the Sample

   1. Cut a section through the blade.

      1. Make the marks on the middle span and the root of the blade as shown in the Engine Manual. Include the arrows on the middle span so the sample is in the correct position when it is attached.

      2. Cut out the sections with a Norton A46M6R50 rubber wheel or equivalent with CoMat 06-088 NITRIDE, AMINE TYPE. Do not let the sample become too hot when you cut it. Carefully put a clamp on the air-cooled airfoils to prevent cracks.

   2. Attach the metallographic sample.

      1. Prepare a mold with a brass tube or equivalent material.

      2. Apply a layer of CoMat 06-119 HIGH TEMPERATURE GREASE, or equivalent, to the inside of the tube.

      3. Prepare a mixture of one part powdered glass to one part liquid epoxy resin. Mix in the applicable catalyst to make the mixture hard.

      4. Put the mixture into the mold and hold each section in the mold. Let the resin become hard at room temperature or in an oven at a maximum temperature of 150 deg F (66 deg C).

      5. Remove the resin from the mold. Bubbles of air at the epoxy-to-sample interface are undesireable.

   3. Polish the sample.

      1. Remove approximately 0.010 to 0.030 in. (0.25 to 0.76 mm) from the surface of the sample with a belt sander with 80 to 100 grit silicon carbide paper. You must use water as the coolant.

         1. NOTE

            As an alternative, you can hand polish.

            Machine polish the sample with 8 in. (203 mm) diameter disks at approximately 550 rpm. Use CoMat 05-021 WATERPROOF SILICON CARBIDE then CoMat 05-019 WATERPROOF SILICON CARBIDE and CoMat 05-064 WATERPROOF SILICON CARBIDE. You can use water if necessary. Use new silicon carbide paper for each micro sample prepared.

      2. Clean the sample with soap and water (or you can use an ultrasonic cleaner with soap and water).

      3. 

         CAUTION

         DO NOT POLISH TOO MUCH.

         Machine polish for one minute at 550 rpm. Use an 8 in. (203 mm) diameter CoMat 05-088 POLISHING CLOTH which contains CoMat 05-091 DIAMOND PASTE and CoMat 10-061 STODDARD SOLVENT. You can hold the sample or it can be mechanically attached.

      4. Clean the sample with soap and water.

      5. 

         CAUTION

         DO NOT POLISH TOO MUCH.

         Machine polish for 15 to 20 seconds at 550 rpm. Use an 8in. (203 mm) diameter CoMat 05-089 POLISHING CLOTH which contains CoMat 05-090 DIAMOND PASTE and CoMat 10-061 STODDARD SOLVENT. You can hold the sample or it can be mechanically attached.

      6. 

         WARNING

         USE PLASTIC CONTAINERS THAT HAVE VENTILATION SO THE PRESSURE DOES NOT BECOME TO HIGH.

         PREPARE THE SOLUTION IMMEDIATELY BEFORE YOU USE IT AND ONLY IN THE NECESSARY QUANTITY. DISCARD THE REMAINING SOLUTION.

         DO NOT MIX THE NEW SOLUTION WITH THE USED SOLUTION. DO NOT PUT PARTS OR SWABS IN THE SOLUTION. THIS WILL PREVENT CONTAMINATION.

         

         CAUTION

         DO NOT ETCH THE SAMPLE TOO MUCH.

         NOTE

         You must use concentrated reagent grade acids to prepare the etching solution. This etching solution has a short life, possibly as low as 24 hours. Make a new solution after 24 hours.

         Swab etch the sample with a mixed acid reagent made of 50 ml of CoMat 01-294 LACTIC ACID, 30 ml of CoMat 01-025 NITRIC ACID HNO3, TECHNICAL GRADE and 2 ml of CoMat 01-027 HYDROFLUORIC ACID until the sample becomes a gold color.

      7. To remove the etch, machine polish for approximately 5 to 15 seconds at 550 rpm. Use an 8 in. (203 mm) diameter CoMat 05-089 POLISHING CLOTH which contains CoMat 05-087 GRIT-ALUMINA as a slurry.

      8. Do Step again.

      9. Clean the sample with water.

      10. Dry the sample.

      11. Examine the surface of the sample to make sure there are no scratches, stains, or relief and that it is correctly etched. If the sample has to be polished again, start the procedure with at least 600 grit. Refer to Step.

2. SUBTASK 70-02-03-220-002 Examine the Microstructure of the Blades

   1. NOTE

      The microstructure of the blade root is not usually changed because of its lower temperature during engine operation. Thus, you can use this structure to compare with hot zone airfoils.

      NOTE

      You do not have to examine areas in each location where there is a coating, or in the coating diffusion zone; examine approximately 0.010in. (0.25 mm) beneath coating diffusion zone.

      NOTE

      The SPM TASK 70-02-10-220-501 can be used to evaluate IAE 1426.

      Examine the microstructure of the blades at three airfoil locations (leading edge, middle chord and trailing edge) and also at the root.

   2. Refer to the applicable turbine blade section in the Engine Manual. Compare the results with the metallographic standards for IAE 1480, IAE 1484, and IAE 1422, (refer to the SPM TASK 70-02-05-220-501, SPM TASK 70-02-06-220-501, and SPM TASK 70-02-10-220-501 respectively). Use 1000X magnification. Report the maximum temperatures found in the specified locations.