High Speed Slurry-Pot Erosion Wear Testing of HVOF and HVAF Sprayed Hardmetal Coatings

Erosion of metallic components is often faced challenge for example in slurry pumps and hydro turbine components. The wear resistance of common metallic alloys can be significantly improved by applying a hardmetal coating by thermal spraying. Two hardmetal compositions (WC-10Co4Cr and Cr3C2-25NiCr) were sprayed with high velocity oxygen-fuel (HVOF) and high velocity air-fuel (HVAF) spray processes. Two carbide sizes were used for both compositions. The coatings were exposed to slurry erosion in a high speed slurry-pot tester with 33 wt% quartz content in water. The HVAF sprayed coatings resulted in a significant improvement compared to HVOF sprayed coatings. Also, the finer carbide size in Cr3C2-25NiCr feedstock material improved the wear resistance compared to the conventional size. The wear resistance of cast 13-4 steel was improved 36 and 180 times by HVAF sprayed WC-10Co4Cr coating when tested with 2-3 mm and 0.1-0.6 mm quartz sands, respectively.