Friction and wear in different engine components have crucial effects on the engine performance, combustion efficiency, oil consumption and lifetime of the internal combustion (IC) engine. Under certain loads, speeds, and temperatures, the metallic components of the IC engine, especially the piston and valve system suffer from a higher friction. Thin film coating is one of the novel techniques to reduce the frictional forces and improve the mechanical properties of engine components. Due to some versatile tribological properties, increasing attention has been paid to the physical vapor deposition (PVD) technology in the recent decade to deposit thin film coating on engine components. This article presents a comprehensive literature review on thin film coatings for IC engine components deposited by PVD technique. Issues related to tribological properties (wear and coefficient of friction) and mechanical properties (hardness and roughness) are also highlighted. Scientific improvements are presented in the light of literature. It is revealed that PVD coating is significantly effective on wear resistance, scuffling resistance, surface roughness, and friction of the components in IC engine. Laboratory test and data from actual service so far suggest that the plasma-activated electron beam evaporation coating is perhaps one of the best choices for smooth surface finishing with improved mechanical and tribological properties. However, there are still some problems in its practical usage. This compressive review paper presents the major shortcomings of PVD coatings on IC engine components and the possible solutions if any. Finally, a number of issues have been reported which need to be encountered for further studies.

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对在不同发动机部件上使用的物理气相沉积涂层的批判性评论

不同发动机部件的摩擦和磨损对发动机性能，燃烧效率，机油消耗和内燃机（IC）的寿命都有至关重要的影响。在某些负载，速度和温度下，内燃机的金属部件（尤其是活塞和阀系统）承受更大的摩擦。薄膜涂层是减少摩擦力并改善发动机部件机械性能的新颖技术之一。由于某些通用的摩擦学特性，近十年来越来越关注物理气相沉积（PVD）技术，以在发动机部件上沉积薄膜涂层。本文介绍了有关通过PVD技术沉积的IC发动机组件薄膜涂层的综合文献综述。还强调了与摩擦学特性（磨损和摩擦系数）和机械特性（硬度和粗糙度）有关的问题。根据文献介绍了科学的改进。揭示了PVD涂层对于IC发动机中的部件的耐磨性，耐擦伤性，表面粗糙度和组件的摩擦具有显着的效果。到目前为止的实验室测试和实际使用的数据表明，等离子体活化的电子束蒸发涂层可能是具有改善的机械和摩擦性能的光滑表面精加工的最佳选择之一。但是，其实际使用中仍然存在一些问题。这份压缩性评论文章介绍了IC发动机组件上PVD涂层的主要缺点以及可能的解决方案（如果有）。最后，