水导轴承等离子堆焊Ni60合金组织及其耐腐蚀性能

采用等离子堆焊技术在Z2CN18-10核电用不锈钢表面堆焊Ni60合金,并研究Ni60合金堆焊层的组织结构、硬度和耐蚀性能。结果表明:堆焊层组织主要由γ-Ni、碳化物、硼化物以及γ-Ni和硼化物的共晶组成,堆焊层的底层、中间层和顶层位置各相体积分数不同,中间层菊花状组织最多。Ni60堆焊层硬度约为500HV,明显高于Z2CN18-10不锈钢基体,菊花状共晶组织有助于提高堆焊层硬度。Ni60在硼酸中的钝化能力明显高于海水,且与Z2CN18-10不锈钢的自腐蚀电位差较小,不易发生电偶腐蚀。在模拟海水中堆焊层中间层耐腐蚀性能优于堆焊层的底部和顶部,与基体的自腐蚀电位差较大,容易出现电偶腐蚀。

Microstructure and Corrosion Resistance of Ni60 Alloy Overlay Deposited by PTA Method on Water Guide Bearing

The Ni60 overlay was deposited on Z2CN18-10 stainless steel substrate by plasma trans-ferred arc(PTA)method,and the microstructure,hardness and corrosion resistance of Ni60 overlay were investigated.The results show that the overlay mainly consists of Ni-rich γ solid solution(γ-Ni),borides and carbides,and γ-Ni and borides eutectic structure.The overlay from the top to bot-tom shows different phase fractions,and the amount of chrysanthemum-like structure in the middle is large.The hardness of Ni60 overlay is around 500HV,which is higher than that of Z2CN18-10 stain-less steel.The hardness increase is attributed to the chrysanthemum-like eutectic structure.In the bo-rate,Ni60 exhibits higher passivation ability than that in seawater,and the corrosion potential of Ni60 alloy is similar to Z2CN18-10 stainless steel.In simulated seawater,the corrosion resistance of over-lay in the middle is more superior than that in the bottom and top.Due to the large difference of corro-sion potential in seawater,the galvanic corrosion is prone to occur between Ni60 overlay and Z2CN18-10 stainless steel.