AZ91D镁合金Ni-W-P多层化学镀层的摩擦磨损及耐腐蚀性能

Friction,Wear and Corrosion Resistance of Multi-layer Electroless Ni-W-P Coating on AZ91D Magnesium Alloy

采用多层化学镀工艺在AZ91D镁合金表面成功制备了Ni-W-P多层化学镀层。通过XRD、SEM、摩擦磨损实验以及电化学分析测试等方法,对比研究了普通单层化学镀试样与多层化学镀试样的显微结构、摩擦磨损性能以及耐腐蚀性能。结果表明:多层化学镀层的摩擦因数、维氏硬度及磨损速率与单层化学镀层大体相当,分别为0.33、933 HV和1.46 mg/Km,保留了单层化学镀层优异的耐磨损性能。此外,多层化学镀层的孔隙率较单层化学镀层降低了2个数量级,涂层更为致密。与普通单层化学镀层相比,多层化学镀层的耐蚀性能显著提高,其腐蚀电位和击破电位分别提高了168和209 mV,钝化电流密度由4.212μA·cm−2降低至1.306μA·cm−2。因此,多层化学镀层有望成为AZ91D镁合金更有前景的耐磨耐蚀防护涂层。

The multi-layer Ni-W-P electroless coating was successfully prepared on surface of AZ91D magnesium alloy.Microstructure, friction, wear and corrosion resistance of both the normal as-plated and multi-layer coatings were investigated comparatively by XRD, SEM, friction and wear tests, and electrochemical experiments. Results show that the wear coefficient,Vickers hardness and wear rate of multi-layer coating are still keeping the same as those of as-plated coating, which are 0.33,933 HV 和 1.46 mg/Km, respectively. The multi-layer electroless coating completely retains the excellent mechanical properties of the as-plated coating. In addition, the porosity of multi-layer coating is two orders of magnitude lower than that of the ordinary as-plated coating, signifying a denser coating for multi-layer electroless coating. Comparing with the as-plated coating, the corrosion resistance of multilayer coating is improved significantly. The corrosion potential(Ecorr) and breakdown potential(Eb) of multi-layer coating are increased by 168 mV and 209 mV respectively, and the passivation current density(icorr) is reduced from 4.212 to 1.306 μA·cm-2. Therefore, multi-layer electroless coating is expected to be a more promising wear-resistant and corrosion-resistant coating for AZ91D magnesium alloys.