Research on Super-smooth Surface Processing of Invar Alloys

Author of the article:WANG Wan1 , WANG Zhijun1 , MA Xiaokang1 , ZHOU Qing1 , XU Quan2 , WANG Yongjie3 , FU Jianming2

Author's Workplace：1. State Key Laboratory of Solidification Processing , Northwestern Polytechnical University , Xi'an 710072 , China ; 2. Shanghai Institute of Mechanical and Electrical Engineering, Shanghai 201109, China; 3. Xi'an Institute of Optics and Fine Mechanics of CAS, Xi'an 710119, China

Key Words：Invar alloy; polishing; precise machining; surface topography; surface roughness

Abstract：In order to achieve ultra-precise machining of high-quality surfaces and improve the polishing quality of Invar alloys, a surface quality study based on multistage polishing technology was conducted. Four polishing states, including coarse grinding, fine grinding, and coarse and fine polishing, were attained by stainless steel polishing disc and automatic polishing machine. The surface morphology, surface roughness, residual stress and surface chemical state of the Invar alloy in each stage were analysed using an optical profilometer, surface 3D profiler, residual stress detector and X-ray photoelectron spectroscopy. The surface components and states during the machining process were further investigated. The results show that the surface roughness of the alloy can be reduced to less than 5 nm, and the surface quality of the workpiece can be greatly improved to achieve a super-smooth surface. The results of X-ray photoelectron spectroscopy show that some Ni and Fe atoms exist in the oxidation state of +2 valence on the surface after polishing, accounting for appximately 21.86% of all atoms. Surface roughness within 5 nm is achieved by multilevel polishing technology, which is of great significance for the ultra-precision machining process of Invar alloys and the improvement of finished product quality.