Abstract
This paper investigated the response of carburized 20CrNi2MoV steel to cryogenic treatment including microstructure and wear resistance. Two cryogenic treatment methods including cryogenic treatment at −80 °C (CT) and deep cryogenic treatment at −196 °C (DCT) as well as conventional heat treatment (CHT) were carried out after carburizing process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD) were employed for microstructure characterization. The wear resistance was investigated by ball-on-disc sliding wear test on a multi-functional tribometer. The results show that the wear resistance of the experimental steel has been improved by 17% due to CT and by 25.5% due to DCT when compared to CHT. This significant improvement in wear resistance after cryogenic treatment is attributed to the microstructural changes including the finer martensitic structure, the reduction of retained austenite and the development of fine and more numerous carbides. Among these factors, the precipitation of fine carbides plays a more prominent role in enhancing wear resistance.
Highlights
Carburizing is a surface-hardening treatment which is usually used to improve the performance of components such as bearings and ring gears which require a very hard surface to resist wear along with a tough interior to resist impact in service [1,2,3,4]
The residual compressive stress exists in the case microstructures of carburized samples as a result of transformation and temperature gradients induced by quenching
The purpose of this paper is to investigate the effect of cryogenic treatment on the microstructure and wear resistance of the carburized 20CrNi2MoV steel
Summary
Carburizing is a surface-hardening treatment which is usually used to improve the performance of components such as bearings and ring gears which require a very hard surface to resist wear along with a tough interior to resist impact in service [1,2,3,4]. The conventional heat treatment (CHT) for carburizing steels is quenching and low temperature tempering. Cryogenic treatment is one of the effective approaches to obtaining better wear resistance of the carburizing steels [13,14,15]. Since the content of RA was no longer changed with the temperature of cryogenic treatment decreasing, there must be other reasons responsible for the improvement of wear resistance. The residual stress existing in the carburized layer still has an effect on the wear resistance. The residual compressive stress exists in the case microstructures of carburized samples as a result of transformation and temperature gradients induced by quenching. The purpose of this paper is to investigate the effect of cryogenic treatment on the microstructure and wear resistance of the carburized 20CrNi2MoV steel. In order to explain the changes of wear resistance, microstructure and worn surface observations were carried out
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