Microstructure and hardness investigation of 17-4PH stainless steel by laser quenching

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• 作者：Zhaoyun Chen ; ^{zhaoyunchenlaoshi@126.com} ; Guijuan Zhou¹ ; ^{zgjghpx@126.com} ; Zhonghua Chen² ; ^{jickdahua@163.com}
• 关键词：Laser quenching ; 17-4PH stainless steel ; Phase transformation
• 刊名：Materials Science and Engineering: A
• 出版年：2012
• 出版时间：1 February 2012
• 年：2012
• 卷：534
• 期：Complete
• 页码：536-541
• 全文大小：1435 K

文摘

Surface hardening of 17-4PH was achieved by laser transformation hardening using 5 kW continuous wave CO₂ laser system. The microstructure of the laser-quenched sample was investigated by optical microscopy, transmission electron microscope and ⁵⁷Fe M?ssbauer spectrometer. The hardness profile was determined by a Vickers hardness tester. The hardened layer with a thickness of 1.75 mm was formed, and it was composed of classic lath martensite, coarse NbC and a lot of finer fcc copper-rich phases which were similar to ?-Cu precipitates. The maximal hardness value of hardened zone is 446 HV which is 50 HV higher than that of the substrate (386-397 HV). The higher hardness in laser transformation layer of the 17-4PH steel could be attributed to the following aspects: the matrix with a high dislocation density; the fine microstructure; the finer fcc copper-rich phases that were similar to the ?-Cu precipitates as well as the transforming of retained austenite into lath martensite.