科研之友
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摘要
As the next generation of high-temperature materials, refractory high entropy alloys (RHEAs) have widespread application potential in aerospace and nuclear fusion fields, where the processing of RHEAs is important for their engineering applications. The cutting performance of WNbMoTaZr0.5 RHEA was studied, as compared with conventional bearing steel GCr15 and die steel Cr12MoV alloys. The effects of cutting parameters and corner radius on the cutting force, surface roughness, machined surface morphology, chip morphology, and chip parameters were analyzed. RHEA showed excellent thermal stability during machining, where the cutting forces and surface roughness have smaller variations with the increase in cutting speed than those of conventional GCr15 and Cr12MoV alloys. Differing from the machining of GCr15 and Cr12MoV, no work hardening was found during the machining of RHEA. Although RHEA had the largest cutting forces because of its high hardness, the surface roughness was relatively low. The influence of cutting depth on the surface roughness of WNbMoTaZr0.5 was small, suggesting that the machining efficiency can be enhanced by increasing the cutting depth without increasing the surface roughness. With the increase in cutting speed, the cutting temperature increased, enhancing the plasticity of the RHEA. This may result in the reduction of the scale-like patterns on the machined surface and the increase of the scale-like pattern size. Serrated chips were observed in the machining of RHEA. With the increase in cutting speed, the gap between shear bands decreased, leading to the concentration of burrs. With the accumulation of secondary shear bands, the internal stress increased, resulting in the rapid expansion of shear bands and the formation of primary shear bands. When the cutting speed was 70 m/min, the light emission phenomenon will be observed. The light emission process will generate burned patterns on the back surface of chips, and the EDS results showed that the elements of the chip surface were redistributed. The effect of cutting parameters and corner radius on the chip parameters in terms of width, thickness, and shear angle was comprehensively analyzed. Finally, adhesive wear was responsible for the main tool wear behavior of RHEA machining. The present findings can provide useful guidance for the machining and practical applications of RHEAs.
