Effect Of Turning On The Surface Integrity And Thermal Stability Of GH4169

Nickel-based alloys have been widely used in the fabrication of critical components in aircraft engine and gas turbine. However, this type of alloys was difficult to machine and the surface integrity after machining had an obvious influence on the service performance and reliability of components. In this dissertation, GH4169 was turned by using the ceramic cutting tool. The effects of the cutting speed and feed on the surface integrity was systematically investigated. The surface integrity parameters included the microstructure near the surface, the work hardening and the residual stress. The evolution of surface integrity under the thermo-mechanical effect was identified. Then, the residual stress relaxation mechanism due to annealing treatment was investigated. The contents and the conclusions were summarized as follows:(1) Both the surface roughness and depth of plastic layer increased, reached local maxima and then decreased with increasing the cutting speed. With increasing the cutting feed, the surface roughness increased. This phenomenon was related to the cutting force, heat-mechanical effect and vibration of workpiece during the cutting process.(2) The work-hardening was obviously found near the machined surface. The micro-hardness and the yield strength decreased gradually with increasing the distance from the surface. The residual stress on the surface increased, reached a local maximum, and then decreased with increasing the cutting speed and feed. The residual stress in the feed direction was higher than that in the hoop direction.(3) Residual stress caused by turning continued to release due to annealing treatment. The Zener-Wert-Avrami model was used to describe the residual stress relaxation mechanism of GH4169...