两种热处理方式对激光焊接钴铬-镍铬异种合金力学性能和组织结构的影响

Effect of different heat treatment on mechanical properties and microstructure of laser welding CoCr-NiCr dissimilar alloys

目的探讨常规热处理和烤瓷对激光焊接钴铬-镍铬异种合金力学性能和组织结构的影响，以期为异种合金的临床应用提供参考。方法将0．5mm厚的钴铬合金和镍铬合金试件各15个从中间断开，进行激光焊接，制成30个钴铬一镍铬异种合金焊件。焊后用随机数字表将焊件随机分为3组，每组10个。对照组不做处理，热处理组焊件进行常规热处理，烤瓷组焊件进行烤瓷处理。测试3组焊件的拉伸强度和延伸率，扫描电镜观察拉伸断口，能谱分析测试3组焊件熔焊区、钴铬焊接交界区和镍铬焊接交界区元素。结果经热处理和烤瓷处理后，焊件拉伸强度分别为（537．15±43．91）MPa和（534．58±48．47）MPa，延伸率分别为（7．65±0．73）％和（7．40±0．45）％。烤瓷组拉伸断口出现明显的韧窝结构，热处理组拉伸断口表现为深而大的韧窝；钴铬侧合金成分向熔焊区和镍铬侧有一定程度的扩散，热处理组比烤瓷组扩散更明显。结论热处理和烤瓷过程均可在一定程度上改善激光焊接钴铬-镍铬异种合金焊接接头的性能，热处理对焊接接头性能的改善比烤瓷更明显。

Objective To evaluate the effect of heat treatment and porcelain-fused-to-metal（PFM） processing on mechanical properties and microstructure of laser welding CoCr-NiCr dissimilar alloys. Methods Samples of CoCr-NiCr dissimilar alloys with 0. 5 mm thickness were laser-welded singleside under the setting parameters of 280 V, 10 ms pulse duration. After being welded, samples were randomly assigned to three groups, 10 each. Gruupl and 2 received heat treatment and PFM processing, respectively. Group 3 was control group without any treatment. Tensile strength, microstructure and element distribution of samples in the three groups were tested and observed using tensile test, metallographic examinations, scanning electron microscope （SEM）, and energy dispersive spectroscopy （EDS） analysis. Results After heat treatment and PFM processing, tensile strength of the samples were （537.15 ± 43.91 ） MPa and （534. 58 ±48.47） MPa respectively, and elongation rates in Group 1 and 2 were （7.65±0. 73 ） % and （7.40 ± 0. 45 ） %. Ductile structure can be found on tensile fracture surface of samples and it was more obvious in heat treatment group than in PFM group. The results of EDS analysis indicated that certain CoCr alloy diffused towards fusion zone and NiCr side after heat treatment and PFM processing. Compared with PFM processing group, the diffusion in the heat treatment group was more obvious. Conclusions Heat treatment and PFM processing can improve the mechanical properties and microstructure of welded CoCr-NiCr dissimilar alloy to a certain degree. The improvements are more obvious with heat treatment than with porcelain treatment.