铁基合金激光熔覆层高温润滑磨损性能

为提高40Cr合金钢的表面耐磨性，采用预置激光熔覆法在40Cr基体表面制备铁基合金涂层， 利用扫描电镜观察分析熔覆层显微组织形貌，用显微硬度仪测试熔覆层截面显微硬度,用摩擦磨损试验机测定在润滑条件下基体、熔覆层的摩擦系数随温度变化的规律。研究结果表明:熔覆层与基体实现良好冶金结合，熔覆层横截面微观组织呈现平面晶、树枝晶和胞状晶分布；熔覆层硬度值介于617.5~926.6 HV0.2之间，基体硬度介于205.2~278.2 HV0.2之间；在200 ℃以下，熔覆层摩擦系数在磨程中趋于平稳，在0.1附近轻微波动，小于基体平均摩擦系数；当温度超过200 ℃，油膜分解，引发润滑失效，磨损方式向干摩擦转化，磨损机理从微切削磨损主导向粘着磨损、磨粒磨损和氧化磨损复合磨损方式转化。

Wear behavior under high temperature and lubrication condition of Fe-based alloy coating formed by laser cladding

In order to increase the wear resistance of 40Cr steel, Fe-based alloy coating was obtained on the surface of 40Cr steel substrate with preset laser cladding technique. The microhardness of both clad coating and substrate were measured by mi-crohardness tester, and the micrographs of clad coating were scanned by SEM. Moreover, wear tests were carried out by wear tester to determine the rule of friction coefficient varying with temperature under lubrication condition. As the tests show, good metallurgical bonding was obtained between Fe-based alloy coating and 40Cr substrate. The microstructure of cross section of the clad coating presents a vertical distribution of planar crystal,dendrite crystal and cellular crystal. The microhardness value of the clad coating fluctuated between 617.5 and 926.6 HV_(0.2),while that of substrate between 205.2 and 278.2 HV_(0.2). Below 200 ℃ , the wear process of clad coating kept stable. The average friction coefficient of clad coating kept at 0.1. As the temperature exceeded 200 ℃ ,the lubrication oil film decomposed and led to lubrication failure, the wear mechanism gradually transformed from micro-scale abrasive wear to adhesion wear, abrasive wear and oxidation wear.