High temperature wear behavior of Co-Mo-Cr-Si hardface coating

The development of suitable hardfacing alloys and advanced deposition processes is needed for thermal power plants that operate at temperatures exceeding 700°C, as is prevailing in advanced ultra-supercritical plants. The hardface coating should provide sufficient hardness, wear, and galling resistance above 700°C. In the present study, a Co-Mo-Cr-Si based hardface coating has been deposited on alloy 617 using plasma transferred arc process. A crack-free coating with a surface hardness of 60.8 ± 1.0 HRC has been achieved. The coating microstructure reveals laves phase present in the cobalt solid solution matrix. The tribological behavior of the coating has been evaluated using a ball-on-disc tribometer from room temperature to 720°C to ensure adequate wear resistance of the developed coating. A decrease in both friction coefficient (0.489–0.196) and wear rate (0.102 × 10 −14 to 0.031 × 10 −14 m 3 /N m) has been observed at 720°C as compared to the room temperature test.