Effect of quenching temperature on microstructure and mechanical properties of new gear steel

doi:10.13251/j.issn.0254-6051.2023.01.028

Abstract

Abstract: Effect of quenching temperature on microstructure and mechanical properties of new gear steel were studied by means of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) combined with tensile test, fracture toughness test and hardness test. The results show that after quenching at 850-1050 ℃, cryogenic treatment and tempering, the tensile strength, yield strength and hardness of the steel increase first and then decrease with the quenching temperature increasing, all reaching the maximum values at 900 ℃ and the tensile strength is 1483 MPa. Moreover, the fracture toughness reaches the maximum value 62.4 MPa·m^1/2 when the quenching temperature is 1000 ℃.The spherical Mo-rich M₆C carbides precipitate on grain boundary and martensite when the quenching temperature is below 1000 ℃. The M₆C carbides dissolve gradually with the quenching temperature increasing, and dissolve completely into the substrate at 1000 ℃. The prior austenite grain size grows slowly with the increase of quenching temperature, when the quenching temperature is above 1000 ℃, the austenite grain coarsens rapidly, the fracture toughness and percentage reduction of area also substantially decrease.

Key words: gear steel, quenching temperature, mechanical properties, microstructure, undissolved phases

CLC Number:

TG142.1

Dai Jianke, Han Shun, Li Yong, Liu Yu, Lei Simin, Wang Chunxu. Effect of quenching temperature on microstructure and mechanical properties of new gear steel[J]. Heat Treatment of Metals, 2023, 48(1): 163-168.

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