Improving the high temperature abrasion resistance of thermally sprayed Cr3C2-NiCr coatings by WC addition

Two experimental agglomerated and sintered (a&s) feedstock powders were prepared, in order to reveal the role of WC addition on the microstructure, hardness, and the abrasion resistance of HVOF-sprayed Cr3C2-NiCr coatings. These powders contained 10 wt.% of sub-micron WC, 20 or 10 wt.% of nickel binder, and Cr3C2 as balance. Experimental coatings were deposited by a liquid fueled high velocity oxygen-fuel (HVOF) spray process and subsequently heat treated at 800 C for 8h to simulate elevated temperature service conditions. The microstructures of powders and coatings were studied by SEM and X-ray diraction, and the hardnesses of coatings were probed by means of micro and nanoindentation. In addition, high stress abrasion resistance was tested in a temperature range from room temperature up to 800 C. The microstructural characterization of coatings Displays the presence of WC and core-rim structured Cr3C2 grains, wherein the rim contains tungsten. The coating hardness increases after the heat treatment, which stems from precipitation of secondary carbides and solid solution strengthening of binder by tungsten. In addition, the study reveals that both experimental coatings have high wear resistance at room and elevated temperatures.