汽车发动机用AZ91镁合金的表面等离子熔凝处理

Surface Plasma Coagulation Treatment of AZ91 Alloy for Automobile Engine

采用等离子熔凝工艺对汽车发动机用AZ91镁合金进行了表面改性处理,分析了熔凝电流对熔凝改性层显微组织、耐磨性能和耐腐蚀性能的影响。结果表明,等离子熔凝层的物相种类与AZ91镁合金基体一致,都为α-Mg和β-Mg17Al12相;熔凝层中的β-Mg17Al12相含量都要比AZ91镁合金基体中多,且随着熔凝电流的增大,熔凝层中的β-Mg17Al12相含量不断增加;电流为45、55和65A时熔凝层的磨损质量损失都要比AZ91镁合金基体低,且随着电流的增大,熔凝层的磨损质量损失逐渐降低;经过等离子熔凝改性后的合金的耐腐蚀性能得到提高,耐腐蚀性能从高至低依次为:65A熔凝层>55A熔凝层>45A熔凝层>AZ91镁合金基体,腐蚀形貌的观察结果与动电位极化曲线的观察结果一致。

Surface modification of AZ91 alloy for automobile engine was carried out by plasma coagulation process,and effects of the current on the microstructure,wear resistance and corrosion resistance of the modified layer were analyzed.The results reveal that the modified layer is composed ofα-Mg andβ-Mg17Al12,which is the same with phase constituent of the AZ91 matrix alloy,however,the phase content in the modification layer is the higher than that in the matrix alloy.With the increase of current,theβ-Mg17Al12 phase content in the modified layer is increased.The wear loss of modification layer with65 A,55Aand 45 Ais the lower than that of AZ91 alloy,and the wear loss of the coating layer is decreased gradually with the increase of current.The corrosion resistance of the alloy is improved after surface modification,and the corrosion resistance of the alloy is as follows：65Acladding layer〉55A cladding layer〉45Acladding layer〉AZ91alloy matrix.The corrosion morphology is consistent with the results of the dynamic potential polarization curves.