Effect of Cryogenic Treatment on the Microstructure and Wear Resistance of 17Cr2Ni2MoVNb Carburizing Gear Steel

Yongming Yan,Zixiang Luo,Xinming Wang,Chen Zhang,Ke Liu,Maoqiu Wang

doi:10.3390/coatings12020281

Yongming Yan, Zixiang Luo + Show 4 more

Open Access

https://doi.org/10.3390/coatings12020281

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Abstract

Cryogenic treatment as a process that can effectively improve the performance of steel materials is widely used because of its simplicity and speed. This paper investigates the effects of different low temperature treatments on the microstructure and properties of 17Cr2Ni2MoVNb steel. The low temperature treatment range is divided into cryogenic treatment (CT-80), shallow cryogenic treatment (SCT-150) and deep cryogenic treatment (DCT-196), all with a duration of 1 h. The retained austenite content and the change in carbide volume fraction at 0.2 mm in the carburised layer are studied. The microhardness gradient of the carburised layer, as well as the friction coefficient and wear scar morphology at 0.2 mm, was investigated. The results show that the low temperature treatment is effective in reducing the retained austenite content and increasing the volume fraction of carbide. The lowest retained austenite content and highest carbide volume fraction were obtained for DCT-196 specimens at the same holding time. Due to the further transformation of martensite and the diffuse distribution of carbides, the microhardness and frictional wear properties of DCT-196 are optimal. Therefore, low temperature treatment can change the microstructure of the case layer of 17Cr2Ni2MoVNb steel and effectively improve the mechanical properties of materials.

Highlights

The 17Cr2Ni2MoVNb steel developed from 18CrNiMo7-6 steel undergoes low distortion during carburizing heat treatment
The changes in the microstructure and mechanical properties of 17Cr2Ni2MoVNb steel subjected to cryogenic treatment at three different temperatures are discussed and compared with those of the sample without cryogenic treatment
After each cryogenic heat treatment process, the samples were subjected to low-temperature tempering at 150 ◦C for 2 h

Summary

Introduction

The 17Cr2Ni2MoVNb steel developed from 18CrNiMo7-6 steel undergoes low distortion during carburizing heat treatment. The main ways to reduce the amount of retained austenite are high-temperature tempering and cryogenic treatment [1,2,3,4]. The effect of cryogenic treatment on the wear resistance of 20CrNi2Mo steel was studied by Preciado and co-workers [5]. There are few reports on the effect of cryogenic treatment on the structure and mechanical properties of 17Cr2Ni2MoVNb steel after carburization. The changes in the microstructure and mechanical properties of 17Cr2Ni2MoVNb steel subjected to cryogenic treatment at three different temperatures are discussed and compared with those of the sample without cryogenic treatment. After each cryogenic heat treatment process, the samples were subjected to low-temperature tempering at 150 ◦C for 2 h

Process Description

Sample CH

Findings

Phase SamplMe artensite Phase