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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655HV_(0.2),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。
Aiming at the high temperature, high alternating stress and high corrosive condition of exhaust valve seat of vehicle internal combustion engine, a nickel-based self-fluxing alloy powder with strong carbide forming elements was added to the CrCuB alloy gray cast iron substrate by laser cladding In-situ synthesized particle reinforced nickel-based composite coatings were prepared. Coating thickness of about 0.6mm, the average hardness of 655HV_ (0.2), metallurgically bonded with the substrate. Hard particles with an average size of about 1μm are uniformly distributed in the coating. The hard particles precipitated from the liquid state combine with the high nickel matrix with low hardness and high ductility to effectively improve the performance of the coating. The results show that the strong tendency of stomatal formation in laser cladding layer on the surface of cast iron is closely related to the existence of graphite phase and the solidification characteristics of nickel base alloy. The reasonable technological measures can eliminate the stomatal defects.