Influence of Plasma Transferred Arc Remelting on Microstructure and Properties of PTAW-Deposited Ni-Based Overlay Coating

Although overlay coatings deposited via plasma transferred arc welding (PTAW) can effectively prolong the service life and improve the performance of components, cracks and pores tend to occur in the high-hardness and wear-resistant coating during the deposition process. Further treatment is thus necessary to improve the coating quality. Herein, PTAW-deposited Ni-based overlay coating was remelted using plasma transferred arc (PTA) under different remelting currents (RCs). The microstructure and phase composition of the coatings were investigated via metallographic microscopy and x-ray diffraction. The hardness, surface quality, and wear resistance of the coatings were also tested. The results show that PTA remelting could effectively eliminate the defects and improve the coating properties when the RC was controlled within a given interval (100-120 A). The type and content of the hard phase in the remelted coating were increased to enhance the microhardness and wear resistance. However, remelting with excessive currents resulted in the agglomeration and growth of the hard phases, which negatively affected the coating hardness and wear resistance. The proper use of PTA remelting technology to treat PTAW-deposited overlay coating is an effective approach for eliminating the coating defects and enhancing the coating properties.