Effect of phase transformation and grain-size variation of hot-pressed cobalt on its dry sliding wear was investigated. The sliding wear test was carried out against glass (83% SiO2) beads at 100N load using a pin-on-disk wear tester. Worn surfaces, cross sections, and wear debris were examined by an SEM. Phases of the specimen and wear debris were identified by an XRD. Thermal transformation of the cobalt from the hcp ε phase to the γ (fcc) phase during the wear was detected, which was deduced as the wear mechanism of the sintered cobalt.

The mixed atomized iron powders with 0.3% graphite and 1% Ni powders were cold pressed and sintered at for 30 min under pure Ar gas atmosphere. Some of the sintered specimens were intercritically annealed at and quenched in water (single quenching). The other sintered specimens were first fully austenized at and water quenched. These specimens were then intercritically annealed at and re-quenched in water. The experimental results showed that the wear coefficient effectively decreased in the double quenched specimen.