Effects of Cryogenic Milling on Stress Corrosion Cracking Resistance of AISI 316L Austenitic Stainless Steel
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JMEPEG https://doi.org/10.1007/s11665-020-05190-1
Effects of Cryogenic Milling on Stress Corrosion Cracking Resistance of AISI 316L Austenitic Stainless Steel Chongwen Yang, Wenqian Zhang, Yujin Hu, and Xuelin Wang (Submitted January 3, 2020; in revised form August 17, 2020; Accepted September 8, 2020) The stress corrosion cracking (SCC) susceptibility of 316L austenitic stainless steel milled with cryogenic cooling and conventional cutting fluid cooling is investigated and compared. The milled subsurface properties are characterized in terms of microstructure, residual stress and microhardness. The SCC susceptibility of the milled surfaces is evaluated in boiling MgCl2 by examining the density and depth of the SCC microcracks. Results show that the cryogenic milling increases the SCC susceptibility of 316L austenitic stainless steel. The increase of SCC susceptibility is attributed to the higher residual tensile stress level and the larger volume fraction of slip band produced in the cryogenic milling process in comparison with the conventional cooling milling. Keywords
cryogenic milling, microstructure, residual stress, stainless steel, stress corrosion cracking
1. Introduction Cryogenically assisted machining is emerging as a clean, safe and environmentally friendly manufacturing process. Liquid nitrogen (LN2) and carbon dioxide (CO2) are the commonly used cryogenic fluids. In recent years, cryogenic machining has been adopted to improve cutting performance and surface integrity of stainless steels and other difficult-tomachine materials. Manimaran et al. (Ref 1) conducted grinding experiments on 316 austenitic stainless steel in three conditions, namely dry, wet and cryogenic cooling. They found that grinding with cryogenic cooling reduced cutting forces, produced lower surface roughness and fewer surface defects, compared to grinding with dry and wet cooling. Kumar et al. (Ref 2) studied the effects of cryogenic condition on AISI 4340 steel turning process. Their results revealed that the cryogenic turning not only reduced cutting forces, but also extended tool life. The surface integrity and corrosion resistance of the 316L austenitic stainless steel machined with cryogenic turning strategy have been investigated (Ref 3, 4). Results indicated that low-temperature coolants introduced more compressive residual stresses and suppressed the initiation of defects on the machined surface, helping to reduce the susceptibility of generalized and localized corrosion. These investigations suggested that the cryogenic machining was able to produce engineered surfaces while reducing damage generated from the machining process. Chongwen Yang, Yujin Hu, and Xuelin Wang, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; and Wenqian Zhang, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; and School of Mechanical Engineering, Hubei University of Technology, Wuhan 430068, China. Contact e-mail: wangxl@
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