PTA overlay is a relatively new process. And it has been spotlighted for its ability to make high functioning overlay layer using high temperature melting powder of alloy and carbide, which previous welding process can not do.
However, to broaden the application of this process, something more is required. That is study of the effect of process variable upon overlay layer, and quantitative analysis of overlay layer's characteristics when this process is used.
Regarding this study, Although it has been reported that Ni-base and Co-base alloy's abrasive behavior upon PTA overlay layer, the effect of high temperature exposure has not been brought to light yet.
So, this study aimed for settling overlay process upon internal-combustion engine's suction, exhaust valve surface based on PTA process. Consequently, we constructed PTA overlay layer on Nimonic material surface using Ni-base super alloy powder, and studied characteristics in micro-structure, abrasion-resistance, abrasion characteristics after high temperature exposure and cavitation resistance upon that overlay layer. Also we examined the cause of hot cracking after PTAW and searched a method to prevent it.