HVOF Tungsten Carbide-Nickel Superalloy
A&A Coatings material is a Tungsten Carbide/Nickel base Superalloy (Metco 5803) specifically developed as a replacement coating for chrome plating. When applied through the HVOF process, this material produces dense, well bonded coatings with a high level of wear resistance. Coatings of this Superalloy resist wear by abrasive grains, hard surfaces and fretting. Field tests have shown coatings to possess fatigue properties equal to or better than chrome plating. Additionally, this material has been qualified to be used under the MIL-STD-1687-A specification as an alternative to chrome plating.
Coatings of this Superalloy have successfully been utilized for the following applications:
- Hydraulic Rods
- Compressor Rods
- Gate Valves
- Ball Valves
- Pump Rotors
- Downhole Drilling Components
These coatings also have excellent submerged salt water corrosion resistance and have completed successful field testing on a large hydraulic steering rod. Salt fog tests (ASTM B117) show the material to have corrosion resistance several times greater than chrome plating.
Material Powder Characteristics
| Typical Composition: | Cobalt 12% Tungsten Carbide Balance Blended with: Nickel Base Superalloy |
Physical Properties of Coating
| Surface Texture As-Sprayed (microinches aa): |
200 – 300 |
| Ground – 150 grit diamond (microinches aa): |
12 – 16 |
| Coating Macrohardness: | Rc55-60 |
| Coating Weight (lb/ft2/.001″): | .056 |
| Bond Strength on Low Carbon Steel Substrate (PSI): |
>12,000 |
Thickness Limitation
A&A Coatings HVOF Sprayed Tungsten Carbide-Nickel Superalloy was designed for use in thin coatings, not more than .5mm (.025″) thick. If sprayed thicker, the probability of cracking and delamination will increase rapidly, as is the case of thick coatings of all fine powders.
Surface Preparation
A&A Coatings HVOF Sprayed Tungsten Carbide is self-bonding to mild steel and to titanium which has been cleaned to remove surface oxides. This cleaning is accomplished with a light grit blast. Preheating of titanium should be done with care, to prevent reformation of surface oxides.
Finishing
In finishing, use standard precision grinding equipment and flood with coolant of water plus 2% soluble oil. The following procedures have produced high finishes:
1. Rough grinding with 150 grit diamond wheels.
2. Finish grinding with 400 grit diamond wheels.
3. Wheel speeds: 1525-1830 m/min (5000-6000 SFPM)
Infeed per pass: .013 mm max. (.0005″)
Work speed:
Cylindrical – 120 m/min (400 SFPM) Flat – Table speed 12 m/min (40 SFPM)
Cross feed:
Flat — 1.3 mm (.050″) per pass, roughing 0.5 mm (.020″) per pass, finishing
Traverse:
Cylindrical — 2.0 mm (.080″) per revolution, roughing 1.0 mm (.040″) per revolution, finishing.