Microstructure and wear characteristics of cobalt-based alloy deposited by plasma transferred arc weld surfacing

The microstructure and wear characteristics of Co-Cr-W series cobalt-based alloys deposited by plasma transferred arc (PTA) weld surfacing were investigated using optical micrograph, X-ray diffraction (XRD), scanning electron micrograph (SEM), transmission electron microscope (TEM) and dry sand abrasion tester (DSAT). Aging effects on the structure and wear resistance of the cobalt-based PTA layer were also studied. It was found that the as-welded coating consisted of a cobalt-based solid solution with face-centered cubic crystal structure and hexagonal (Cr,Fe)7C3. There were lots of stacking faults existing in the cobalt-based solid solution. After aging at 600 °C for 60 h, another carbide M23C6 with face-centered cubic crystal structure precipitated. Although the precipitation of carbide M23C6 can increase the hardness, the coarse of the microstructure and the change of the morphology led to the increase of the wear weight loss.