COMMERCIAL ENGINE STANDARD PRACTICES MANUAL

	COMMERCIAL ENGINE STANDARD PRACTICES MANUAL	Dated: 04/01/2013
	SPM 70-49-38 ELECTRIC-ARC WIRE SPRAYING NICKEL ALUMINUM (WIRE)

TASK 70-49-38-340-037

1 .

General.

Nickel-aluminum alloy is used either to form a bond with various top coat systems, or for dimensional buildup of metal.

NOTE:

The material is available as powder for plasma arc spraying per TASK 70-49-10-340-011, Thermal Spraying Nickel-Aluminum (Powder), and as wire for flame spraying per TASK 70-49-11-340-012, Thermal Spraying Nickel-Aluminum (Wire), or electric arc spraying. Those procedures are acceptable alternatives.

Arc wire spraying consists of an electric arc which is struck between two feed wires resulting in complete melting of the wire and subsequent deposition of the molten atomized droplets on the part. The molten droplets are atomized and delivered to the part by a stream of air. The material is self-bonding, has a high bond strength, and can be deposited at high deposition rates in excess of 10-20lbs/hr.

2 .

Equipment.

Subtask 70-49-38-340-371

The equipment to do electric-arc wire spraying consists of the following.

(1)

An arc-wire gun utilizing dual wire feed capable of melting, atomizing and depositing the molten droplets on the work piece.

(2)

An arc-wire gun control unit that is capable of delivering spooled wire to the arc gun unit either manually or automatic with pneumatic or electrically driven motors. The unit shall also provide gun power control and air delivery rate.

(3)

An electric-arc wire power supply that is capable of 50-350 amps at 20-38 open circuit volts.

(4)

A clean filtered air supply that is capable of delivering 50 SCFM at 80 psi (552 kPa).

Commercially available equipment.

Model 8830, 8835, 8850, or 9000

Available from Praxair/TAFA Concord.

SmartArc™

Available from Sulzer Metco.

Refer to the List of Suppliers in Step 4 of TASK 70-80-00-800-803.

3 .

Material.

Subtask 70-49-38-340-372

NOTE:

Nickel-aluminum wire material should have a chemical composition to GE Specification B50TF56, Class A, except Total Other Elements (1)----1.7 Max., and conform to the physical requirements of GE Specification B50TF69, Class A, except the wire diameter shall be 0.0625 in. (1.59 mm) nominal with spools up to 25 lb (11.34 kg) permitted.

Nickel-Aluminum Wire C07-042 .

4 .

Spraying Parameters.

Subtask 70-49-38-340-373

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 70-49-38-340-374

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 1.

(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 1. 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 1. Porosity shall be uniformly distributed.

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. If this coating is applied in a thickness range up to 0.015 inches (0.38 mm), the tensile bond strength for this coating at room temperature shall average 5,000 psi (34.5 MPa), minimum. If this coating is applied in a thickness range greater than 0.015 inches (0.38 mm), the tensile bond strength for this coating at room temperature shall average 4,000 psi (27.6 MPa), minimum.

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.