Effect of copper oxides on defect formation during PTA cladding of Stellite 6 on copper substrates

Abstract

Stellite 6 coating is ideal for the protection of copper components in high-temperature environments, but the quality of the coating can be affected by the formation of copper oxide at the interface. In this study, plasma transfer arc cladding was employed to prepare Stellite 6 alloy cladding layers on copper substrates, with a preheating temperature of 700 °C and a cladding current of 120–170 A. Cladding experiments were conducted to investigate the impact of copper oxides generated during the cladding process on the quality of the cladding layer. Results showed that, when the current was below 140 A, insufficient current input caused edge cracking of the cladding layer, and the cracks tend to extend along the oxide layer at the interface. Interfacial reactions between the Stellite 6 alloy and copper oxide on the copper substrate produced CO/CO2, which led to pores forming at the interface. When the current was above 140 A, the localized overheating resulted in the upturning of the substrate, destroying the continuous copper oxide layer and eventually forming localized dents. The copper oxide affects the bonding of the cladding layer to the substrate. Increasing the cladding current helps to eliminate cracks and porosity, resulting in a good bond, but excessive current leads to localized dents. In this paper, 140 A was a relatively suitable current to produce satisfactory cladding layers. The wear resistance of the cladding layer was 1.9 and 2.2 times higher than that of the copper substrate at 25 and 300 °C, respectively.