Influence of the metallic matrix ratio on the wear resistance (dry and slurry abrasion) of plasma sprayed cermet (chromia/stainless steel) coatings

This work is related to the manufacturing and tribological testing of plasma sprayed cermet coatings of chromium oxide and stainless steel in order to obtain wear resistant coatings to dry and slurry abrasion. Raw materials were fused and crushed powders of chromium oxide (Cr2O3) with a particle size ranging from 20 to 45 μm and gas atomized stainless steel (iron base with 17 wt.% of Cr and 12 wt.% of Ni) with a particle size distribution between 20 and 53 μm. Both powders were simultaneously injected with two separated injectors in a direct current (DC) plasma jet (Ar–H2 (25 vol.%) at atmospheric pressure (APS).The influence, on the coating micro-structural and tribological properties, of various stainless steel weight percentages in chromium oxide has been studied. All coatings exhibited a lamellar structure with a random distribution of the two materials. The effect of the percentage of stainless steel on the microstructure of the coating, studied by scanning electron microscopy (SEM), has shown that increasing the stainless steel percentage increased the coating cohesion. The increase of Cr2O3 in the coatings resulted in higher hardness and in lower weight losses during wear tests in dry abrasion. The study has also shown that the optimum stainless steel percentages in coatings were not identical to reach their maximum resistance to slurry or dry abrasion.