Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Wenjun Song,Chaowen Huang,Min Lei,Mingpan Wan

doi:10.3390/met11010048

Wenjun Song, Chaowen Huang + Show 2 more

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https://doi.org/10.3390/met11010048

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Abstract

In this study, the phase transformation behaviour of the carburised layer and the matrix of 23CrNi3Mo steel was comparatively investigated by constructing continuous cooling transformation (CCT) diagram, determining the volume fraction of retained austenite (RA) and plotting dilatometric curves. The results indicated that Austenite formation start temperature (Ac1) and Austenite formation finish temperature (Ac3) of the carburised layer decreased compared to the matrix, and the critical cooling rate (0.05 °C/s) of martensite transformation is significantly lower than that (0.8 °C/s) of the matrix. The main products of phase transformation in both the carburised layer and the matrix were martensite and bainite microstructures. Moreover, an increase in carbon content resulted in the formation of lamellar martensite in the carburised layer, whereas the martensite in the matrix was still lath. Furthermore, the volume fraction of RA in the carburised layer was higher than that in the matrix. Moreover, the bainite transformation kinetics of the 23CrNi3Mo steel matrix during the continuous cooling process indicated that the mian mechanism of bainite transformation of the 23CrNi3Mo steel matrix is two-dimensional growth and one-dimensional growth.

Highlights

IntroductionMo series low-carbon alloy steel [1]
23CrNi3Mo steel, which is widely used to make hollow drill rods, is a kind of Cr–Ni–Mo series low-carbon alloy steel [1]
Their dilatometric curves coincided in the early heating content of of the the carburised sample and theoriginal origistage, 1

Summary

Introduction

Mo series low-carbon alloy steel [1]. Cr–Ni–Mo series low-carbon alloy steel has generated interest from drilling tool practitioners and scholars [3,4,5]. Various surface engineering techniques that can endow additional useful surface properties, such as high strength and wear resistance, have been devised to meet this demand [6]. Among these techniques, carburizing heat treatment is one of the most widely applied to improve steel hardness and strength [7,8,9]

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