U71Mn钢表面激光熔覆Ni60-25％WC涂层工艺参数优化的研究

目的研究U71Mn钢表面激光熔覆Ni60-25%WC涂层的最佳工艺参数。方法首先通过单道单因素试验初步选取激光功率、送粉量、扫描速度和光斑直径4个工艺参数,然后进行4因素3水平的单道正交试验,以熔覆层的宽度、高度和稀释率作为判断熔覆层质量的指标,做极差分析,最后得到最优工艺参数并分析了熔覆层的显微硬度及显微组织。结果单道单因素试验及单道正交试验得到的工艺参数均为:激光功率1500 W,送粉量4 g/min,扫描速度6 mm/s,光斑直径2.2 mm。通过单道正交试验极差表分析发现,工艺参数对质量指标的影响程度不同,对熔覆层宽度的影响为扫描速度送粉量激光功率光斑直径,对熔覆层高度的影响为送粉量扫描速度光斑直径激光功率,对熔覆层稀释率的影响为送粉量光斑直径扫描速度激光功率,对比发现送粉量是熔覆层的最大影响因子。熔覆层的显微硬度最高可达到1170HV,是基体的3.7倍。结论在U71Mn钢表面激光熔覆Ni60-25%WC涂层,可以制备出光滑且紧密结合的熔覆层,且表面硬度明显提高。

Optimization of Process Parameters of Laser Cladding Ni60-25%WC Coating on U71Mn Steel

The work aims to study optimum process parameters of laser cladding Ni60-25%WC coating on U71Mn steel surface. First, single-channel single-factor test was performed to preliminarily select four process parameters, namely, laser power (A), powder feeding rate (B), scanning speed (C) and spot diameter (D). Then, single-channel orthogonal test involving 4 factors and 3 levels was completed. Range analysis was done with cladding layer width, height and dilution ratio as criteria of cladding layer quality. Finally, optimum process parameters were obtained, microhardness and microstructure of the cladding layer were analyzed. The process parameters obtained from the single-channel single-factor test were: A=1500 W, B=4 g/min, C=6 mm/s and D=2.2 mm. The optimum process parameters by single channel orthogonal experiment showed that A=1500 W, B=4 g/min, C=6 mm/s, D=2.2 mm; the range analysis showed that degree of effect of process parameters on quality criteria was different. For effect on cladding layer width, the order was C>B>A>D; for effect on cladding layer height, B>C>D>A; and for effect on dilution ratio of cladding layer, B>D>C>A. Comparison showed that powder feeding rate was the dominating impact factor of cladding layer. The microhardness of cladding layer was up to 1170HV, which was 3.7 times of that of substrate. A smooth and closely-bonded cladding layer can be prepared, and surface hardness is increased obviously by laser cladding Ni60-25%WC coating on U71Mn steel surface.