Hardening of Thermally Sprayed WC-CrC-Ni Cemented Carbide Layer by Friction Stir Processing

Abstract

Friction stir processing of a thermally sprayed WC-CrC-Ni cemented carbide layer was carried out to clarify the optimum conditions for obtaining a hardened layer without any cracks and pores. Although cracks and pores were observed in the cemented carbide layer after friction stir processing at a forging load of 4.9 kN, friction stir processing at a higher forging load of 9.8 kN or 14.7 kN could eliminate these defects. The amount of pores was decreased owing to rearrangement of WC particles by the stirring effect. The cracks were suppressed by densification of the cemented carbide layer and the martensitic transformation of the SKD61 substrate during cooling. When the forging load was 14.7 kN, the hardness of the cemented carbide layer reached to 2200 HV. On the other hand, friction stir processing at 19.6 kN caused large plastic deformation of the SKD61 substrate and cracks occurred in the cemented carbide layer on the advancing side.