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

这项合作由福特加拿大公司和不列颠哥伦比亚大学奥卡纳根分校合作，旨在提高下一代汽车发动机的效率和性能。该项目的成功完成可以帮助汽车业实现政府严格执行的到2025年每加仑54.5英里的燃油经济性目标。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)发动机机体的制造过程中，材料性能的差异会导致许多有害问题的产生，包括但不限于产生残余应力(即在没有外部载荷的情况下锁定在材料中的应力)。这些问题削弱了材料，主要是由于发动机机体中使用的铁(Fe)衬里的存在，以保护较软的铝基材料免受磨损。为了缓解铁衬里的缺点，制造商已经开始使用耐磨涂层。福特是最早实施等离子转移焊丝电弧(PTWA)涂层工艺的先驱之一。尽管它在2011年款野马燃气轮机中证明了它的健壮性，但我们的初步研究证实，在PTWA过程中发生的快速热传递仍然会导致高达100兆帕的拉伸残余应力的产生。此外，相对较厚的涂层导热性较差，导致气缸峰值温度较高，从而导致发动机效率下降。因此，开发了一种新的方法，即电解喷射等离子体氧化(EJPO)，该方法通过最小化应用过程中产生的温度梯度来降低残余应力的积累。因此，本研究旨在研究涂层工艺对福特新款V8发动机机体残余应力的影响。此外，还将检测新的EJPO涂层的表面纳米孔隙率、保油性和耐磨性，以确定将EJPO涂层用于新发动机批量生产的可行性。

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.