关键词: 整体叶轮, 工艺参数, 表面完整性, 铣削

Abstract:  Based on the real machining parameters， this paper investigated the effects of milling speed， feed per tooth， stepover， milling depth and coolant on the surface integrity of the integral impellers， which includes the aspects such as surface roughness， surface morphology， surface microhardness， microstructure and residual stress. The results show that stepover and feed per tooth have the most significant influence on the surface roughness， the smaller stepover and feed per tooth value result in smaller blade surface roughness. Specifically， when the stepover is decreased from 0.3 mm to 0.16 mm， the average roughness value reduces from 0.64 μm to 0.48 μm； as the feed per tooth is decreased from 0.1 mm to 0.06 mm， the average roughness value decreases from 0.62 μm to 0.4 μm. Both of the stepover and feed per tooth significantly impacts the surface morphology. As the stepover and feed per tooth increase， the row spacing residual height and feed residual height also increase. Since the selected machining parameters are relatively reasonable， blade surface is observed to be smooth without the production of defects such as scratches， scrapes， and burrs， etc. Moreover， under the reasonable machining parameters， the generated force and heat are insufficient to alter the surface microhardness， which fluctuates around 335HV for each machining parameters， leading to no distinct difference in the surface hardening layer compared to the substrate. The residual stresses observed are predominantly compressive stresses， with limited correlation to the stepover and milling depth. When considering the milling speed and feed per tooth， the surface compressive stress initially increases and 
then decreases. Along the depth direction， compressive stress initially slightly decreases， reaches a peak， and finally stabilizes within the matrix. The maximum residual stress reaches to 275 MPa and 400 MPa in the parallel and perpendicular feed directions， respectively. Surface residual stress under the water-based coolant is much higher than that under the oil-based coolant， but decreases significantly in the depth direction. 

Key words: integral impeller, machining parameter, surface integrity, milling