等离子喷涂灰铸铁涂层的研究进展

在汽车上使用轻质铝合金发动机可以有效减少燃油消耗和环境污染,但铝合金的耐磨损性能较差,从而造成发动机工作过程中气缸壁面容易磨损。利用表面改性技术对铝合金表面进行强化处理,可以满足其作为滑动部件在高载荷条件下的使用要求。灰铸铁较低的成本和其中石墨的自润滑作用,使其成为铝合金发动机气缸表面保护涂层材料的首选。等离子喷涂技术以其高效率和灵活性在表面强化领域受到广泛应用。因此,利用等离子喷涂制备灰铸铁涂层成为改善铝合金发动机气缸表面耐磨性的有效方法之一。但是,由于等离子喷涂过程中熔滴冷却速度极快,等离子喷涂很难得到含大量石墨组织的灰铸铁涂层。以调控灰铸铁涂层中的石墨含量为目的,总结了等离子喷涂灰铸铁涂层的研究现状,以及基体温度、颗粒尺寸、添加合金元素等对熔滴冷却速度的影响,并以此为基础,结合凝固理论分析了在涂层中保留灰铸铁粉末中的石墨组织的可行性,同时分析了在铸铁涂层中保留石墨所面临的主要问题,并提出了解决这些问题的主要措施。最后就在等离子喷涂灰铸铁涂层中保留石墨的研究方向进行了展望。

Research Progress of Gray Cast Iron Coating Prepared by Plasma Spraying

Objective The use of light aluminum alloys engine in the automobiles can effectively reduce fuel consumption and environmental pollution. However, the poor wear resistance of aluminum alloys is easy to cause the severe surface wear of aluminum alloys cylinder bore during working. Surface modification technology can be used to strengthen the surface of aluminum alloy, which can meet the requirements of the aluminum alloys sliding parts under high load conditions. The self-lubricating effect of graphite and low cost of grey cast iron make grey cast iron as the preferred material for protecting coating of the cylinder surface of aluminum alloys engines. Plasma spraying technology has been widely used in the field of surface hardening due to its high efficiency and flexibility. Therefore, plasma sprayed gray cast iron coating has become one of the effective ways to improve the wear resistance of the aluminum alloy engine cylinder surface. However, it is difficult to precipitate the graphite crystal in coating owing to the rapid cooling of melting particles during deposition. The purpose of this paper is to discuss the controlling of the graphite content in gray cast iron coating. The research status of plasma spraying gray cast iron coatings and the effect of substrate temperature, particle size and elements addition on cooling rate were introduced and summarized. On the basis of above reports and solidification theory, the feasibility of reserving the graphite in the coating was analyzed. The major obstructions for reserving the graphite in gray cast iron coating were also analyzed. Finally, the future research direction of reserving graphite in the plasma spraying gray cast iron coating was prospected.