A&A Coatings - Model HVOF -Chromium Carbide Coatings Material
A&A Coatings material is a blend (75/25) of very fine particles of chromium carbide and nickel chromium powders. When properly sprayed using the HVOF process, it produces coatings which are very hard, dense and well bonded. Because of its unique combination of properties, HVOF Chromium Carbide is recommended for resistance to wear by fretting, abrasive particles and hard surfaces in the temperature range 540°- 815°C (1000°-1500°F).
HVOF Chromium Carbide coatings are dense (less than 1/2 volume percent porosity) and well bonded (tensile bond strength in excess of 12,000 psi, 83 MPa). These coatings, however, may be best characterized by their high macro and microhardness which translates into excellent high temperature wear resistance.
A&A Coatings HVOF Sprayed Chromium Carbide was designed for use in thin coatings, not more than .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 PreparationA&A Coatings HVOF Sprayed Chromium 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.
FinishingHVOF coatings may be used for many applications with no subsequent finishing, due to its fine as sprayed texture. If finishing is required, an excellent finish can be obtained utilizing green silicon carbide or diamond grinding wheels with rust inhibiting water- based coolant, using the following procedures:
- Coolant: Use flood coolant of water with 2% rust inhibitor oil
- Wheel: GC60-H11-VR
- Wheel Speed: 25-30 m/s (5,000-6,000 SFPM)
- Table Speed: Roughing – 12 m/min (40 SFPM)
- Finishing – 6 m/min (20 SFPM)
- Traverse Speed: Roughing – .5mm (.020″)
- Finishing – .25-.5mm (.010-.020″)
- Infeed Per Pass: Roughing – .013-.025mm (.0005-.001″)
- Finishing – .005-.013mm (.0002-.0005″)