TASK 70-49-15-340-016
1 . General.
Nickel-graphite blend forms a moderately heat resistant coating for clearance control applications. It is available in powder form for flame spray application.
2 . Equipment.
Subtask 70-49-15-340-161
A.Refer to TASK 70-49-00-340-001, Thermal Spraying.
3 . Material.
Subtask 70-49-15-340-162
A.85:15 Graphite Powder C07-015  .
4 . Spraying Parameters.
Subtask 70-49-15-340-163
A.Starting parameter sets will be listed in the spray equipment manuals or are readily available from the spray equipment manufacturers or powder suppliers. Modifications may be necessary for your location and product application. See sprayability testing per TASK 70-49-00-340-001, Thermal Spraying, and TASK 70-70-00-700-001, Testing and Quality Analysis. When the final spray parameter settings are developed, all values should be recorded to ensure consistent achievement of high quality coatings.
5 . Quality Assurance.
Subtask 70-49-15-340-164
A.Thickness.
Measure the coating thickness using a standard flat-anvil-and-spindle micrometer. The measurement may be made on either a coated production part or on a flat test specimen having a thickness of at least 0.060 inch (1.52 mm). Determine coating thickness to the nearest 0.001 inch (0.03 mm) at three different locations.
B.Appearance.
Visual examination of the coating shall be in accordance with the following:
(1)Adhesion.
The coating shall exhibit no spalling or lifting.
(2)Coverage.
The coating shall exhibit complete, uniform coverage in those areas specified for coating in the Engine/Shop Manual. Coating is not permissible in areas other than those specified.
(3)Surface condition.
The coating shall be uniform and free from cracks, blisters, spatter, chipping, and flaking.
C.Coating Microstructure.
When specified by the Engine/Shop Manual, test specimens shall be prepared for microscopic examination, and evaluated in accordance with TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings. Metallographic examination of the prepared specimen shall be made for uniformity of coating, as well as for the following other conditions:
(1)Delaminations.
The coating shall be free of delaminations as defined for metallic coatings in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings.
(2)Integrity.
The coating shall show acceptable integrity as defined in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings.
(3)Transverse Cracks.
The coating shall be free of transverse cracks as defined for metallic coatings in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings.
(4)Phase.
Phase shall be identified as defined in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings, and then rated per the guidelines of Table 1.
D.Tensile.
Tensile specimens shall be prepared for tensile bond testing and evaluated in accordance with TASK 70-71-01-700-002, Bond Strength Tensile Testing of Thermal Spray Coatings. Tensile bond strength for this coating at room temperature shall be 1,200 psi (8.3 Mpa) minimum to 3,000 psi (20.7 Mpa) maximum.
E.Macrohardness.
Test specimens will be prepared for Rockwell hardness testing. The specimen material may be of a convenient size or shape, but it should be at least 0.030 inch (0.76 mm) thick and of the same material as the coated part. The specimen must be coated with sufficient material to meet the thickness values of the part, the thickness values that are specified in TASK 70-49-00-340-001, Thermal Spraying, or the thickness requirements in TASK 70-34-03-220-009, Rockwell Hardness Testing, and ASTM E-18 (whichever results in the maximum thickness). The Rockwell hardness range for this coating shall be 50-70, based on an average of at least ten readings on a Rockwell R15Y scale. For this coating, the specimen should have a top coat thickness of .080 inch(2.03 mm), minimum.
 
Acceptance Limits for Thermal Spray - Table 1
 
Feature
Acceptance Criteria
Rating Photograph
Task
Comments
 
Phase
Nickel content shall not exceed View 2 or be less than View 1
Figure 26
TASK 70-71-04-700-005
None
 
Transverse Cracks
None allowed
No figure for rating
TASK 70-71-04-700-005
See definition for ratable size
 
Delamina-tions
None allowed
No figure for rating
TASK 70-71-04-700-005
See definition for ratable size