针对车用内燃机排气门座圈高温、高交变应力和高腐蚀性工况,采用添加了强碳化物形成元素的镍基自熔合金粉末,通过激光熔覆,在CrCuB合金灰铸铁基体上制备了原位合成的颗粒增强镍基复合涂层。涂层厚度约0.6mm,平均硬度655HV0.2,与基体成冶金结合。平均尺寸约1μm的硬质颗粒在涂层中均匀分布,这种从液态合成析出的硬质颗粒与具有低硬度高塑性的高镍基体强韧结合,能有效提高涂层的使用性能。研究表明,铸铁表面镍基合金激光熔覆层产生气孔的强烈倾向与石墨相的存在和镍基合金的凝固特征密切相关,合理的工艺措施可以消除气孔缺陷。

The Center of Laser Process Research,Department of Mechanical Engineering,Tsinghua University,Beijing 100084,ChinaThe exhaust valve ring of the vehicle internal-combustion engine works in extreme conditions,with high temperature、frequent periodic stress and corrosion. Adding strong-carbide-formation elements to Ni-based self-fluxing alloy powder,composite coatings were obtained,which were reinforced by in-situ synthesized particles on CrCuB alloy gray iron substrate by laser cladding. The coatings with thickness of about 0.6mm,hardness of 655HV0.2,have strong metallurgic bonding with the substrate. Uniformly distributing in coatings,hard particles of about 1μm in size is combined with the high contained Ni substrate characterized by low hardness,high plasticity,which effectively improve the wearing resistance of the coatings. The results show that,there is strong gas porosity tendency in the generating Ni-based composite coatings which were reinforced by laser cladding on the surface of alloy iron. That has strong relative with the existence of graphite phase and solidifying character of Ni-base alloy. Reasonable technical methods can be used to eliminate the gas porosity.