Plasma Chromium Oxide
A&A Coatings material is a chromium oxide powder for spraying with the Plasma Spray Process. It was designed to produce dense, hard, wear resistant coatings. The coatings also have excellent self-mating and anti-galling properties. This material is recommended for resistance to wear by abrasive grains, hard surfaces, particle erosion and cavitation, all at temperatures below 540 ̊C (1,000 ̊F). These coatings are insoluble in acids, alkalis and alcohol. When properly sealed, they are recommended for use in corrosive chemical environments in temperatures up to 177-205 ̊C (350-400 ̊F). Additionally, these coatings can also be useful in the textile industry on any machine element which comes into contact with fibers and threads, where a relatively coarse, brush finished, hard, wear and corrosion resistant ceramic coating is required.
Material Powder Characteristics
|Typical Composition:||Chromium Oxide 98%|
|Typical Size Range:||-170 mesh +15 microns|
|Melting Point:||2435°C (4415°F) approximate|
Physical Properties of Coating
|Texture, as sprayed, (microinches RMS):||350 – 550|
|Finish, ground (microinches aa):||15 – 35|
|Macrohardness:||Rc65 – Rc72|
|Cross-Sectional Hardness (DPH300):||900 – 1200|
|Coating Weight (lb/ft2/.001″):||.027|
|Bond Strength on Low Carbon Steel (psi)||4000|
A&A Coatings Plasma Sprayed Chromium Oxide exceeding 0.8mm (.030”) have been applied to the outside surface one-inch diameter mild steel shaft, without any signs of spalling or delamination. However, coatings of this material are dense and should be restricted to thicknesses less than 0.6mm (.025”), especially for flat surfaces and inside diameters.
Ground finishes of Chromium Oxide coatings were achieved using a 150 grit diamond wheel, and the recommended feeds and speeds associated with grinding flame sprayed ceramic coatings (available by request).
Lapped finishes were obtained using standard metallographic polishing techniques for ceramic coatings.
Brush finished coatings can be produced using standard equipment and techniques. The following brush finishes were obtained:
|2-5 minute brushing||220-290 RMS|
|5-10 minute brushing||150-200 RMS|
|10-15 minute brushing||140-160 RMS|