中文摘要：

利用激光辅助直接金属沉积技术在1018低碳钢上沉积Co-285单壁墙，并利用优化参数制得大面积沉积层。利用光学显微镜、附带能谱仪的扫描电镜、X射线衍射仪、显微硬度计和磨损试验机研究沉积单壁墙或沉积层的显微组织、成分、物相、横截面的显微硬度分布和耐磨性。结果表明：沉积的单壁墙无气孔和裂纹等缺陷，成形性能良好，且与基体形成冶金结合；单壁墙由枝晶和枝晶间共晶组成；所有工艺参数下单壁墙的硬度相差不大；当激光功率为0．8kw、送粉率为8．6g／min、扫描速度为0．375m／min时，单壁墙硬度值最大，达到407HV0．5；在此参数下制得沉积层的组织与单壁墙的类似，其相组成为α-Co固溶体、富Cr的M23C6和C03w；磨损60min后，沉积层体积损失为1．4mm^3；磨损机制为研磨磨损、粘着磨损和氧化磨损的混合磨损。

英文摘要：

The laser-aided direct metal deposition （LADMD） technique was used to fabricate Co-285 single walls on 1018 mild steels, and large scale coatings were fabricated with optimal parameters. The microstructure, composition, phases, microhardness of the cross-sectiun and wear resistance of the deposited single walls or coatings were analyzed by OM, SEM, XRD, microhardness tester and wear tester. The results indicate that the deposited single walls prepared with different parameters are pore and crack free, with good processability. A metallurgical bonding exists between the walls and substrates. The deposited single walls are composed of dendrites and eutectics, and the microhardness under different parameters varies a little, among which the highest hardness is 407HV0.5 when the laser power, powder flow rate and laser scanning speed are 0.8 kW, 8.6 g/min and 0.375m/min, respectively. The coating fabricated with the above parameters has the same structure as the deposited single walls, and the phases are a-Co solid solution, Cr-riched M23C6 and Co3W. After wear for 60min, the wear volume loss of the coating is 1.4 mm^3, the wear mechanism is a mixture of abrasive, adhesive and oxidation wear.