Analysis and Optimization of Electrolytic Jet Plasma Oxidation (EJPO) Coating for Manufacturing of High-Efficiency Automotive Engines

福特加拿大公司和英属哥伦比亚大学奥肯那根分校的合作旨在提高下一代汽车发动机的效率和性能。该项目的成功完成将有助于汽车行业在2025年之前实现政府严格执行的54.5 MPG燃油经济性目标。为了实现这一目标，有必要研究发动机轻量化的新方法和/或开发新的制造工艺，以消除降低或限制发动机热效率的已知问题。在铝（Al）发动机缸体的制造过程中，材料性能的差异会导致许多有害问题的发展，包括但不限于残余应力的产生（即在没有外部负载的情况下被锁定在材料中的应力）。这些问题削弱了材料，主要是由发动机缸体中用于保护较软的Al基材料免受磨损的铁（Fe）衬垫的存在引起的。为了减轻铁衬垫的缺点，制造商已经开始使用耐磨涂层代替。福特是最早采用等离子转移电弧（PTWA）涂层工艺的公司之一。尽管在2011款野马GT中证明了它的坚固性，但我们的试点研究证实，PTWA过程中发生的快速传热仍然会导致高达100MPa的拉伸残余应力的产生。此外，相对较厚的涂层导热性差，导致较大的峰值气缸温度，从而导致发动机效率下降。因此，开发了一种新的方法，即电解射流等离子体氧化（EJPO），该方法通过最小化其应用过程中产生的热梯度来降低残余应力的积累。因此，本研究旨在表征涂层工艺对福特新款V8发动机缸体残余应力的影响。此外，还将对新型EJPO涂层的表面纳米孔隙度、保油性和耐磨性进行测试，以确定EJPO涂层用于新发动机量产的可行性。

This partnership, between Ford Canada and the University of British Columbia Okanagan, aims to improve the efficiency and performance of the next generation of automotive engines. The successful completion of this project could help the automotive industry meet the strict governmentally enforced fuel economy target of 54.5 MPG by 2025. To accomplish this goal, it is necessary to investigate new methods of lightweighting the engine and/or developing new manufacturing processes to eliminate known issues that lower or restrict the thermal efficiency of the engine. During the manufacturing process of aluminum (Al) engine blocks, differences in material properties cause a number of harmful issues to develop, including but not limited to the generation of residual stress (i.e. stress that is locked in the material without an external load). These issues weaken the material and are primarily caused by the presence of the iron (Fe) liners that are used in engine blocks to protect the softer Al base material from wear. To alleviate the drawbacks of the Fe liners, manufacturers have begun using wear-resistant coatings instead. Ford was one of the early pioneers to implement a coating process known as plasma transferred wire arc (PTWA). Although it proved its robustness in the 2011 Mustang GT, our pilot study confirmed that the rapid heat transfer that occurs during the PTWA process still leads to the generation of the tensile residual stress of up to 100MPa. Moreover, the poor thermal conductivity of the relatively thick coating results in larger peak cylinder temperatures which lead to a decrease in engine efficiency. Thus, a newer method, electrolytic jet plasma oxidation (EJPO), was developed which has the potential of lowering the accumulation of residual stress by minimizing the thermal gradients produced during its application. Thus, this study aims to characterize the effects that the coating processes have on the residual stress in Ford's new V8 engine block. Moreover, the surface nano-porosity, oil retention, and wear resistance of the new EJPO coating will be examined to determine the feasibility of using EJPO coating for mass production of the new engine.