激光熔覆纳米La2O3添加镍基合金涂层的耐磨与显微组织研究

本研究以激光工艺制备了添加纳米La2O3初料的镍基涂层。激光熔覆之前，高能球磨机充分混合的Ni60A和La2O3粉床预置于基体30CrMnSiNi2A表面。La偏聚于枝晶间从而限制了二次枝晶的成长和熟化。显微组织得到了细化。由于更高的La富集，涂层上表面显微组织细化更为显著，这一现象的上述解释得到EPMA结果佐证。同时EPMA结果说明Fe稀释会造成涂层硬度降低。熔覆涂层经过RE显微组织细化和净化，硬度、耐磨性均相对基体金属显著提升，而涂层中裂纹和孔隙均未出现。Ni60A-La涂层的摩擦系数曲线COF明显低于基体和Ni60A涂层，Ni60A-La磨擦体积损失率分别少于基体和Ni60A涂层数值的1/10和1/5，显微硬度值是基体4倍。

Wear Resistance and Microstructure of Laser Cladded Ni-based Coatings with nanometer La2O3 Addition

Ni-based coatings with nano-sized feedstock rare earth element (RE, La2O3) addition were produced by laser cladding. Bed of high energy ball milling mixed Ni60A and La2O3 powders were pre-placed unto the substrate 30CrMnSiNi2A before laser cladding. La segregates in interdendrite thus secondary dendrites growth and ripening are limited. The microstructure is refined. Top surface of cladded coatings displayed better refined microstructure which caused by high La concentration, this phenomena is verified in EPMA results. And the results of EPMA reflected the interconnection between Fe dilution and decrease of coating microhardness. The cracks and pores cannot be found in cladded coatings in which microstructure refinement and purify effect caused by RE is clearly reflected in SEM microstructure, hardness and especially, the wear resistance test results. The COF of Ni60A-La coatings is apparently lower than substrate steel and Ni60A, the wear volume loss rate of Ni60A-La coatings is less than 1/10 that of 30CrMnSiNi2A and 1/5 that of Ni60A, respectively. The microhardness of Ni60A-La is about 4 times higher than that of substrate metal.