COMMERCIAL ENGINE STANDARD PRACTICES MANUAL

	COMMERCIAL ENGINE STANDARD PRACTICES MANUAL	Dated: 04/01/2015
	SPM 70-49-48 HIGH DENSITY HVOF T-400 (TRIBALOY) COATING

TASK 70-49-48-340-047

1 .

General.

Tribaloy T-400 material is normally applied by Air Plasma Spray (APS) per TASK 70-49-27-340-028, Thermal Spraying Cobalt-Molybdenum-Chromium-Silicon Alloy (Powder) - Tribaloy 400, on surfaces in the HPT and LPT sections of the engine that are prone to fretting wear. This procedure describes the application of pre-alloyed Tribaloy T-400 powder by the high velocity oxy fuel (HVOF) process.

HVOF spraying is a combustion process using a suitable fuel gas such as oxygen/hydrogen, oxygen/propylene or kerosene which is ignited under a pressure of 35-125 psi (242-863 kPa). Powder is introduced axially or radially into the flame, melted, and accelerated onto the substrate at a high velocity, 2000-5000 ft/sec (60690-152400 cps). The deposits produced have a bond strength greater than 9,000 psi (62190 kPa), a density of almost 100 percent, and can be deposited much thicker than conventional combustion or plasma processes. The material is self-bonding and is deposited at a rate of 4 to 8 lbs/hr (1.8 and 3.6 kg/hr). A higher rate of deposit is possible.

2 .

Equipment.

Subtask 70-49-48-340-471

The equipment to do high density HVOF spraying consists of the following:

(1)

An HVOF gun system with a suitable controller.

(2)

A gas controller that can deliver up to 1,000 SCFH oxygen, 1600 SCFH hydrogen, 300 SCFH propylene, and if required, 800 SCFH air. If liquid fuel is used, an appropriate controller is required. The unit shall provide gun power control and air delivery rate.

(3)

A pressurized powder feeder that can deliver powder between 4-15 lbs/hr (2-7 kg/hr).

(4)

A clean filtered air supply that can deliver up to 800 SCFH.

Commercially available equipment consists of the following:

Model

Address

Jet Kote 2000

Stellite Coatings Deloro Stellite, Inc. Refer to the List of Suppliers in Step 4 of 70-80-00.

Diamond Jet 2600 Hybrid

Sulzer Metco, Inc. Refer to the List of Suppliers in Step 4 of 70-80-00.

JP-5000

Praxair/TAFA Concord. Refer to the List of Suppliers in Step 4 of 70-80-00.

3 .

Material.

Subtask 70-49-48-340-472

NOTE:

Powders may be sieved to meet spray requirements for the equipment used.

Co-Mo-Cr-Si Powder C07-025 .

4 .

Spraying Parameters.

Subtask 70-49-48-340-473

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. For initial recommendations see Table 1.

Spray Parameters - Table 1

Gases

Manifold Pressure

Flow Rate (SCFH)

Primary: Oxygen

105±2 psi (725±14 kPa)

560±7

Fuel: Hydrogen

115±2 psi (794±14 kPa)

1240±15

Carrier: Helium

90±2 psi (621±14 kPa)

10±2

Powder Rate:

22±4 grams/min

Standoff Distance:

6.0±1.0 in. (152±25 mm)

Traverse Rate:

3.0-4.0 in./sec

(76-102 mm/sec)

Part Rotation:

200-400 fpm (6-12 mps)

Thickness per Pass:

0.0002-0.0010 in.

(0.005-0.025 mm)

Part Temperature:

150-300°F (66-148°C)

Water Cooling:

Water Inlet:

95-105°F (35-41°C)

Water Outlet:

125-135°F (52-57°C)

Line Pressure:

180±10 psi (1242±69 kPa)

Maximum Substrate Temperature:

Steel:

400°F (204°C)

Titanium:

300°F (148°C)

Aluminum:

300°F (148°C)

Recommended Thickness: 0.0030-0.0300 in. (0.076-0.762 mm).

5 .

Quality Assurance.

Subtask 70-49-48-340-474

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.

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.

Coating Microstructure.

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)

Interface Separation.

The coating shall be free of interface separations as defined in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings.

(4)

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.

(5)

Interface Contamination.

Interface contamination in the coating 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 2.

(6)

Oxides and Oxide Clusters.

Oxides in the coating shall be identified as defined in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings, and then rated as described in the guidelines of Table 2. The coating shall be free of oxide clusters as defined in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings. Oxides shall be uniformly distributed.

(7)

Porosity.

Porosity in the coating shall be classified for size as defined in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings, and then rated per the guidelines of Table 2. Porosity shall be uniformly distributed.

(8)

Unmelts.

Unmelts in the coating shall be classified for size, shape, and bonding as defined in TASK 70-71-04-700-005, Metallographic Evaluation of Thermal Spray Coatings, and then rated per the guidelines of Table 2.

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 8,500 psi (58.6 MPa) minimum.

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 0.060 inch (1.52 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 for this coating shall be 83 minimum, based on an average of at least five readings on a Rockwell R15N scale. No individual specimen shall have a reading of less than 81.

Microhardness.

Test specimens shall be prepared for microhardness testing. Test specimens shall meet a minimum average hardness DPH (Vickers) 500 using a 300 gram load. The specimen shall be prepared and tested in accordance with TASK 70-34-02-220-008, Vickers Hardness Testing, or ASTM specification E384. No individual specimen shall have a reading of less than 400.

Bend Test.

The technical requirement for this test has been deleted and no longer needs to be performed when specified in the Engine/Shop Manual.