Effects of the Ambient Temperature and Load on the Wear Performances and Mechanisms of H13 Steel
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I.
INTRODUCTION
THE wear of materials is a complicated process; the wear mechanisms and performances are closely related with the sliding speed, contacting stress, ambient temperature, microstructures and properties of materials, etc.[1–3] During the dry sliding wear of steels, the ambient temperature and load are important factors deciding the wear performance. The physical and chemical properties of steels on worn surfaces change with increasing the ambient temperature and load. It is well known that the elevation of the ambient temperature and load readily lead to forming a tribo-oxide layer on worn surfaces. In addition, a high ambient temperature and load would cause an obvious plastic deformation in the matrix of steels due to the reduced strength of steels. The tribo-oxide layer on worn surfaces and the plastic deformation in the subsurface both have obvious influence on the wear performances and wear mechanisms of steels.[4] Sullivan studied the wear behaviors of 52100 low alloy steel under various ambient temperatures.[5] As the temperature was higher than 573 K (300 C), the wear mechanism turned into oxidation wear. Clark et al. found that, with increasing the temperature, the wear rate reduced due to the structural variation of the tribo-oxide layer.[6] Many other researchers reported that the oxide layer formed on worn surfaces played a major role in M.X. WEI and F. WANG, Postdoctoral Students, and S.Q. WANG and Y.T. ZHAO, Professors, are with the School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, P.R. China. Contact e-mail: [email protected] Manuscript submitted September 12, 2009. Article published online May 26, 2011 3106—VOLUME 42A, OCTOBER 2011
protecting steels from wear at elevated temperatures.[7,8] Lim et al. took the sliding speed and load as the independent variables to classify the wear into mild and severe wear with transition zones in between, and established the wear transition maps of steels under dry sliding friction.[9,10] Ashby studied the influence of the worn-surface temperature on the wear and built up the thermal wear map.[11] He considered that, as the sliding speed and load exceeded the critical values, the wear mechanism was determined by the interface temperature, at which some processes, such as oxidation, phase transformation, and melt, would occur. When the temperature on the worn surface was relatively low, the wear was mainly determined by the deformation degree of materials. So it was considered that adhesive and abrasive mechanisms prevailed at a low speed that led to a low temperature on the worn surface. Under the nominal pressures larger than 4.4 MPa and sliding speeds greater than 3 m/s, the wear loss mainly resulted from the plastic extrusion and the wear became severe. Between these two extremes, there was the regime of oxidation wear.[12] The aim of this research is to investigate the effects of the ambient temperature and load on the wear behavior and wear mechanism of H13 steel. More importantly, the roles of tribo-oxides and
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