铝合金表面激光熔覆镍基复合涂层的组织与磨损性能

Microstructure and wear properties of Ni-based composite layer on aluminum alloy by laser cladding

摘要:

利用SEM、EDS、磨损试验机及硬度测试仪等设备对铝合金表面激光熔覆层的组织与磨损性能开展了研究。结果表明当扫描速度为5mm/s时，熔覆层气孔、裂纹等缺陷相对较少；在熔覆层顶部生成了许多块状及网状的Ni-Al金属间化合物，中部生成了(Ni, Cr, Fe)XCy金属间化合物，底部存在大量具有明显生长方向性的柱状α-Al枝晶。熔覆层顶部及中部保持着高硬度值，中部硬度最高值达820HV，是熔覆层底部硬度值的5倍以上。硬度值在熔覆层中部的末端开始显著下降。熔覆层的摩擦系数根据载何不同其值在0.37-0.43间，并随着载荷增加而有所降低。主要原因是Ni-Al和(Ni, Cr, Fe)XCy金属间化合物等强化相在熔覆层中生成及其均匀分布在熔覆层的中上层改善了材料的硬度及磨损性能。

Abstract:

The microstructure and wear properties of Ni-based composite coatings on aluminum alloy by laser cladding were investigated by means of SEM, EDS, a microhardness tester and friction tester. The results showed that the holes and cracks are relatively few in the layer when the scanning speeds of 5 mm/s.Many massive and continuous network Ni-Al intermetallic compounds formed at top of the cladding layer, and (Ni, Cr, Fe) XCy intermetallic compounds were formed at the middle of the cladding layer. The microstructure of the bottom cladding layer consisted of the columnar α-Al dendrite with obvious growth direction. The middle and the top of the cladding layer maintained a high microhardness value. The microhardness of the middle of layer had a maximum value of 820HV, which was more than 5 times that of the bottom of the cladding layer. The microhardness decreased sharply at the end of the middle of layer. The friction coefficients of the layer have a fluctuation with the different of load, and it decreased with the load increasing. The Ni-Al and (Ni, Cr, Fe) XCy intermetallic, forming and distributing on the top and middle of the cladding layer were the primary reason for the improvement of the microhardness and wear of the layer.