Effect of Rare Earth Upon As-Cast Microstructure and High Temperature Performance of ZA40 Alloy
In testing comparison, this study is made on the modification effect of 0.05 wt.% La-rich rare earth (RE) upon as-cast microstructure, mechanical properties of materials at high temperatures (100, 150, 200°C) and wear resistance under different temperatures (100and 200°C) of ZA40 alloy containing Si. The addition of RE shows that it can not only effectively refine Al-rich and Cu-rich phase, but also reduce the amount of needle-like eutectic silicon, and then make the size of massive primary silicon phase smaller. Thus, there are the improvement of strength, ductility and wear resistance of materials at high temperature. The analyses are also conducted on the mechanism of underlying RE elements.
Research on the wear characteristics of hypereutectoid steel
Abstract In this research, the wear behavior of hyper-eutectoid steel was examined at ambient temperature ranging from room temperature to a high temperature of 400 °C. A common asymmetric test rig was used, where a pin specimen of hyper-eutectoid steel is pressed against a disk of carbon steel for machine structure use. Two types of pin specimen were prepared: an as-received specimen and a quenched specimen.. As a result, the following was clarified. The protective surface film of iron oxide is not a main factor in determining the wear behavior of the hyper-eutectoid steel of as-received pin specimens. The wear behavior is closely related to the separation of the oxide film from bulk material when the sliding conditions are severe. The wear behavior of a quenched pin specimen is strongly influenced by a microstructural transition and a reduction in hardness of the pin specimen at elevated temperature.
Effects of additives on wear mode and morphology of wear debris generated in the lubricated sliding of steel
Abstract The predominant wear mechanisms were studied as a function of contact pressure and sliding velocity in thin-film-lubricated sliding under conditions of concentrated contact with a hard chromium steel ball from the view point of additives. Three kinds of lubricants were used in this study: (1) alkylnaphthalene oil (base oil), (2) base oil plus 0.044 wt.% stearic acid and (3) base oil plus 1.0 wt.% tricresyl phosphate (TCP). The results were arranged in the form of a wear mode diagram. The effects of additives on the diagram and morphology of wear debris generated in each wear mode regime were studied and discussed. It was found that additives contributed to the ability to achieve mild flow wear. The degree of contribution was as follows: TCP > stearic acid > base oil. The shape of wear debris generated did not depend on the kind of additive in each wear mode regime; however, the size was strongly dependent on the kind of additive.