Microstructure dynamic evolution of 17-4PH stainless steel aged at 480 ℃

doi:10.13251/j.issn.0254-6051.2020.08.005

Abstract

Abstract: 17-4PH stainless steel forged rod was solid solution treated with oil cooling, and aged at 480 ℃ for 0-5 h with air cooling. Microstructure evolution and mechanism of precipatate hardening in the aging process were observed and analyzed by means of optical microscopy (OM), ultra-depth-of-field microscopy, XRD and microhardness tester. The effect of dynamic aging precipitation process of ε-Cu phase on electric resistance was indirectly tested by resistor, and the wear resistance was tested by friction and wear tester. The results show that there are no retained austenite and reversed austenite observed in the solid solution and aging process of the 17-4PH stainless steel. After heat treatment, there are two martensite morphologies i.e. lath and block. The hardness of lath martensite is higher than that of block one. With the prolongation of aging time, the hardness of both martensite increases synchronously. Aging precipitation obviously increases the hardness of solution treated structure. Aging for 2.0-2.5 h, the hardening effect and wear resistance are the weakest in the vicinity, which may be related to the growth of ε-Cu phase and the interaction with dislocation. Meanwhile, the change trend of hardness is opposite to that of resistance.

Key words: 17-4PH stainless steel, martensite, microstructure, electric resistance, hardness

CLC Number:

TG178

Xie Wenfei, Wu Wenyun, Wang Donghong, Yang Lianjin, Wu Riming. Microstructure dynamic evolution of 17-4PH stainless steel aged at 480 ℃[J]. Heat Treatment of Metals, 2020, 45(8): 22-26.

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