Effect of Cryogenic Treatment on Microstructure and Wear Resistance of Carburized 20CrNi2MoV Steel

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.

Quantification of the Dislocation Density, Size, and Volume Fraction of Precipitates in Deep Cryogenically Treated Martensitic Steels

“…Deep cryogenic treatment (DCT) is a sub-zero treatment where materials are exposed to temperatures below −125 • C with liquid nitrogen being the preferred cooling media [1]. Deep cryogenic treatment on martensitic steels is commercially carried out to improve wear resistance [2][3][4][5][6][7], and it has also been reported to affect other material properties such as hardness [8][9][10][11][12][13][14][15][16][17][18][19][20] and tensile strength [21][22][23]. There are some proposed mechanisms for these improvements in the literature.…”

“…The transformation of retained austenite (RA) to martensite is one of the primary objectives of DCT, and it is one of the predominating proposed mechanisms for improvement in wear resistance, as the martensitic phase is much harder than the parent austenite phase [2,4,19]. This transformation has regularly been quantified and verified via X-ray diffraction (XRD) [3,4,19,22,[24][25][26][27][28][29][30]. However, it has also been observed that alloys that are already fully martensitic can exhibit markedly improved wear resistance after DCT, even though there is no change to the martensite volume fraction [31]; this is commonly referred to as the conditioning of the martensite [32].…”

Impact of Mechanical Processes as a Pre-Sulphonitriding Treatment on Tribology Properties of Selected P/M Tool Steels

“…The abrasive wear resistance was evaluated by well-known pin-on-disc method [20,21]. More information about the mechanical tester and how the measurements were conducted have been provided in earlier papers [22,23].…”

Microstructure and Abrasive Wear Resistance of Various Alloy Hardfacings for Application on Heavy-Duty Chipper Tools in Forestry Shredding and Mulching Operations

“…However, the obtained improvement of the properties due to the application of heat treatment was relatively small. When selecting appropriate material for working in abrasive wear conditions, the criteria generally considered are the material hardness and microstructure [16,17,18,19,20,21]. However, there is no unified opinion among researchers on the most beneficial type of material microstructure in terms of its abrasive wear resistance.…”