通过激光直接沉积成形技术制备不同Mo元素含量的Cr-Ni不锈钢, 对工艺参数进行优化, 并对Cr-Ni不锈钢合金进行成分设计与组织性能评价。采用半导体激光器直接沉积成形15Cr21Ni7双相不锈钢合金粉添加xMo(x＝0%、1%、2%、3%、4%), 在激光功率1 800 W, 激光扫描速度5 mm/s, 搭接率30%, 送粉率8.9 g/min的优化工艺参数下获得了长宽高分别为10 mm×10 mm×4 mm的不锈钢块体样品。利用光学显微镜、电子探针、X射线衍射仪、显微硬度计及电化学测试系统进行了沉积层的显微组织、成分、物相及显微硬度、耐蚀性分析。实验结果表明, 沉积层无气孔和裂纹等缺陷, 成形性良好; 沉积层的中部稳定, 显微组织主要由岛状枝晶、奥氏体枝晶和枝晶间区域为铁素体、奥氏体、合金碳化物的混合组织组成; 随Mo含量的增加, 沉积层的耐蚀性随Mo含量的增加先升高后降低, 当Mo含量达到3%时, 耐蚀性获得最高值: 自腐蚀电流密度为167.21 nA/cm2, 自腐蚀电位为－142.26 mV。沉积层的显微硬度随Mo含量的增加变化不大, 其平均显微硬度在340～390 HV。

The Cr-Ni stainless steels with different content of Mo were prepared by the Direct Laser Deposition (DLD) technology in this paper. The DLD processing parameters were optimized and the compositions of the duplex phase stainless steels were designed and the microstructure and performance were also evaluated. The 15Cr21Ni7 duplex phase stainless steel alloy powder adding with xMo (x＝ 0%, 1%, 2%, 3%, 4%) was deposited by a semiconductor laser. The samples with the length of 10 mm, the width of 10 mm and the height of 4 mm were prepared. The optimization of parameters with the laser power of 1 800 W, the laser scanning speed of 5mm/s, the overlapping rate of 30%, and the powder feeding rate of 8.9 g/min, respectively were used. The optical microscopy, electron probe microanalysis (EPMA), X-Ray Diffraction (XRD), microhardness tester and electrochemical test system were used to analyze the microstructure, composition, phase, microhardness and the corrosion resistance of the DLD 15Cr21Ni7-xMo stainless steel specimens. The results showed that no defects such as porosity and cracks were found in the deposition layers. The microstructure of the DLD 15Cr21Ni7-xMo was mainly composed of the island austenite dendrite and ferrite, austenite, alloy carbides in the dendrite region. The corrosion resistance of the DLD 15Cr21Ni7-xMo steels first increased and reached the highest value at Mo=3 wt.% then decreased with the further increase of content of Mo. The self-corrosion current density was 167.21 nA/cm2 and self-corrosion potential was-142.26 mV of the specimens with Mo content of 3%. The microhardness of the DLD 15Cr21Ni7-xMo steels changed little with the increase of the content of Mo that the average microhardness were about 340 HV to 390 HV.