Low Load Wear of Aluminum Alloys

点击翻译按钮获取中文摘要

Evaluation of the wear rate of power train components in automobiles is crucial to the choice of materials, and their design and construction in the production of durable engines. Wear rates of nanometers (nm) per hour (nm/hr) are required in modern automobiles. Conventional testing methods are not capable of the necessary sensitivity for laboratory tests that run for only a few hours under conditions that mimic engine conditions. Accelerated testing is generally not applicable as wear rates can exhibit drastic changes with applied load, sliding velocities etc; these are the so called wear-rate transitions which make extrapolation of wear rates from one set of conditions to another essentially impossible. Measurements at low loads (< 10 Newtons; N) are particularly difficult as the wear rates are very low in practice, for example in a cylinder bore. With the development of new lightweight materials (eg Al-Si alloys) for cylinder bores, it is essential to develop methods of measuring lubricated wear rates at relevant loads, sliding velocities and temperature, in tests that only last a few hours. Earlier methods required activation of the material to be tested. The technique was effective, but produced radioactive material for disposal. Thin layer activation resolves the disposal problem but relies on activation by ions in the 5 to 100 MeV range. The current proposal brings together experts in wear and friction, in antiwear additives such as the zinc dialkyl dithiophospates (ZDDPs), and nanoscale materials analysis to develop new methods based upon the creation, by MeV ion implantation, of a known depth profile of an element that can be neutron activated and analyzed by neutron activation analysis (NAA). The method will only produce short lived isotopes and hence greatly alleviate the disposal problem. The project will permit the evaluation of nm/hr wear rates on Al-Si alloys, determine the efficacy (or even the necessity) of ZDDP antiwear agents at low loads, and investigate other lubricant packages. The information will be applied by General Motors of Canada Ltd. (henceforth GM) to the design of power train components.