Abstract
Wear resistance of metallic materials can be effectively improved by the deep cryogenic treatment. In this study, different deep cryogenic treatment conditions were considered, with different soaking durations between quenching and tempering. The main objective is investigating the effects of deep cryogenic treatment and exploring the relationship between the mechanical properties and the microstructure of GB 35CrMoV steel. Hardness and relative wear ratios of samples were evaluated by the Vickers-hardness test and the pin-on-disk wear test, respectively. Worn surface was characterized by a non-contact optical surface profiler. Microstructures were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). Significant improvements in hardness and wear resistance are observed for higher cryogenic soaking times; the root mean square deviation (RMS) parameter (Sq) was employed to evaluate the effect of deep cryogenic treatment on the worn surface roughness; the improvements were ascribed to the precipitated carbides. The mechanism can be interpreted not only as the promoted effect of deep cryogenic treatment in the decomposition kinetics of martensite, but also as the acceleration on the Ostwald ripening process.
Highlights
Podgornik et al [15] investigated the effect of deep cryogenic treatment on the wear resistance of different tool steels, and suggested that the improvement in properties can be related to the formation of finer needle-like martensite and the martensitic transformation accompanied by plastic deformation of primary retained austenite
Reference material used in this investigation was commercial GB 35CrMoV steel, which is a mid-carbon steel commonly used in the industry due to its high fatigue limit, high static strength and good creep strength
The root mean square deviation (RMS) parameter (Sq) indicated that the degree of smoothness of worn surface was improved with the prolonged deep cryogenic treatment time
Summary
Over the last several decades, deep cryogenic treatment has been recognized as an effective method to improve hardness, fatigue, toughness and wear resistance of metallic materials [1,2,3,4]. Podgornik et al [15] investigated the effect of deep cryogenic treatment on the wear resistance of different tool steels, and suggested that the improvement in properties can be related to the formation of finer needle-like martensite and the martensitic transformation accompanied by plastic deformation of primary retained austenite. Das et al [16] demonstrated that the improvement of wear resistance by deep cryogenic treatment of AISI D2 steel samples was unambiguously related to both the substantial modification in the precipitation behavior of secondary carbides and the reduction in retained austenite content. Yan et al [17]
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