热处理对钛基化学镀Ni-P镀层性能的影响

Effects of heat treatment on properties of Ni-P coating on titanium alloy

为了改善钛合金耐磨性,利用化学镀法在钛基表面获得Ni-P合金镀层,着重考察了热处理温度对镀层腐蚀和磨损性能的影响。采用XRD、SEM、EDS等手段分析了镀层的结构、表面形貌及组成。通过磨损量和在HCl溶液中极化曲线分析了镀层的耐蚀和磨损性能。结果表明,镀态下镀层是胞粒状堆积形式,属非晶结构,磷含量为6.9wt%;随着热处理温度变化其耐蚀性存在最佳值,250℃×1h热处理后的Ni-P镀层,在1mol/L HCl溶液中的腐蚀电流和腐蚀电位分别为0.0129mA/cm2和-0.427V,耐腐蚀性能优于其它镀层;镀层硬度随热处理温度的升高先增加后降低,磨损量则呈相反趋势,400℃硬度达到最高值960.5HV,磨损量最低值达到15.6mg,此时镀层为晶态结构,表面呈弥散状态;热处理可提高钛基化学镀层的耐磨性。

Ni-P alloy coating on titanium alloy was obtained by electroless plating method in order to improve the wear resistance of the titanium alloy. The influence of annealing temperature on the corrosion and the wear performance of the Ni-P coating was investigated. The structure, morphology and composition of the coating were analyzed by using XRD, SEM and EDS. The corrosion and the wear properties of the coating were studied by polarization curve measurements in HCl solution and by wear test, respectively. The resuhs show that the Ni-P coating before annealing is cellular amorphous structure. The phosphorus content is 6.9wt %. After annealing at 250 ℃ × 1 h, the corrosion potential is - 0. 427V and the corrosion current density is 0.0129mA/cm^2 which is smaller than that of the coatings annealed at other temperatures. The hardness of the coating increases first and then gradually decreases with the increasing of annealing temperature and opposite change of the wear mass loss is observed. The hardness reaches a peak value of 960.5HV and the wear mass loss is 15.6mg at 400 ℃. After annealing at the temperature, the coating shows a crystal structure and the compounds in the coating is in a dispersed state. The test results show clearly that the wear resistance of Ni-P coating on the titanium alloy can be improved by means of heat treatment.