钛合金化学镀镍-磷前后处理对镀层耐蚀性能的影响

Effect of Substrate Micro-Arc Oxidation and Coating Heat-Treatment at Lowered-Temperature on Corrosion Resistance of Electroless Nickel-Phosphorous Coating of Titanium Alloy

为了提高TC4钛合金化学镀镍-磷层的耐腐蚀性能,对TC4基材化学镀前作微弧氧化处理和化学镀后作低温热处理,采用中性盐雾法研究了其腐蚀性能。结果表明:TC4钛合金表面微弧氧化、化学镀镍-磷后作再热处理,镀层的耐蚀性能最好,达8级;直接化学镀后再热处理镀层的耐腐蚀性为5级,不经热处理镀层的耐蚀性能最差,仅为1级;微弧氧化和低温热处理均能大大提高化学镀镍-磷层的耐腐蚀性能。

Micro-arc oxidation of TC4 Ti alloy substrate was combined with post heat-treatment of electroless Ni-P coating at lowered temperature so as to improve the corrosion resistance of the Ti alloy substrate. The corrosion resistance of as-obtained Ni-P alloy coatings was evaluated based on neutral salt-spray test. It was found that,after Ti alloy substrate was pre-treated by micro-arc oxidation while electroless Ni-P coating prepared on the pre-treated Ti alloy surface was post heat-treated,resultant Ni-P coating possessed the best corrosion resistance( the anticorrosion performance was ranked as grade 8). After Ti alloy substrate was directly electroless plated with Ni-P coating and heat-treated at lowered temperature,corresponding electroless Ni-P coating exhibited moderate corrosion resistance( the anticorrosion performance was ranked as grade 5). However,as-plated Ni-P alloy coating showed the poorest corrosion resistance( the anticorrosion performance was ranked as only grade 1). In one word,both micro-arc oxidation of Ti alloy substrate and lowered-temperature heat-treatment of electroless Ni-P coating favored to significantly improve the corrosion resistance of the coating.