能量密度对内燃机用Ti600表面激光熔覆Ni-Co涂层组织及耐蚀性的影响

Effect of Energy Density on the Microstructure and Corrosion Resistance of Laser Cladding Ni-Co Based Coating on Ti600 Surface for Internal Combustion Engine

为了提高内燃机用Ti600表面的耐蚀性能,对Ti600合金实施激光熔覆处理制得Ni-Co涂层,测试分析了能量密度对Ni-Co涂层组织及耐蚀性的影响。结果表明:在涂层内形成了(Ni,Co) Ti2.5组织以及α-Ti组织结构。当激光能量密度降低后,涂层保持基本稳定的物相结构,而涂层中的各组织相都形成了更大的半峰宽。更大的激光能量密度可降低涂层晶粒尺寸。当激光能量密度降低后,形成了更大的涂层混合熵。Ni-Co涂层内部有孔洞,但涂层与基体结合良好。Ni-Co涂层形成了比Ti600合金更宽范围的钝化区域,具备更优的耐点蚀性能,设定更大激光能量密度可以提升涂层耐蚀性。在NaCl与H2SO4共同组成的混合溶液中,涂层依然形成了明显的钝化区,表现出良好的钝化性能。

In order to improve the corrosion resistance of Ti600 surface for internal combustion engine,the Ni-Co coating was prepared by laser cladding on Ti600 alloy. Subsequently,the effects of energy density on the microstructure and corrosion resistance of Ni-Co coating were analyzed. Results showed that( Ni,Co) Ti2.5 structure and α-Ti structure were formed in the coating. When the laser energy density decreased,the coating maintained a basically stable phase structure,and each tissue phase in the coating presented a larger half-peak width. In addition,higher laser energy density could reduce the grain size of coating. When the laser energy density decreased,a greater entropy of coating mixing was formed. The Ni-Co coating had some holes inside,but the coating well adhered to the substrate. The Ni-Co coating formed a wider range of passivation region than Ti600 alloy,and so the better pitting resistance was obtained. Moreover,setting a larger laser energy density could improve the corrosion resistance of coating. In the mixed solution composed of Na Cl and H2SO4,the coating still formed an obvious passivation zone,showing good passivation performance.