比粉与比能对激光熔覆NiWC25特性的影响

目的探究激光熔覆过程中比粉和比能对合金粉末与基体的结合特性、熔覆层宏观形貌和微观结构、熔覆层最大宽度和结合宽度比值的影响规律,找出熔覆层既无柱节结构又具有良好冶金结合的比粉和比能的可选范围。方法采用正交实验和单一控制变量相结合,制备出一组单道熔覆层,分析该熔覆层比粉和比能对柱节结构、临界结合结构、均匀圆柱结构的影响特性。结果当激光熔覆的比粉大于7vs/mm、比能大于200ws/mm时,熔覆层最大宽度与熔覆层结合宽度的比值大于1.41,熔覆层和基体之间出现间隙,使熔融合金粉末在熔覆过程中沿着垂直于基体方向塌陷,形成了明显柱节结构的熔覆层;当比能为200 ws/mm、比粉小于5vs/mm时,熔覆层的宏观形貌为均匀圆柱形结构,且熔覆层最大宽度与基体和NiWC25的结合宽度比值为1;当比粉大于7 vs/mm、比能小于100 ws/mm时,NiWC25和基体出现临界熔覆层,甚至出现基体和熔融Ni WC25合金粉末脱离现象。结论只要激光熔覆的比粉在3～5 vs/mm、比能在100～200 ws/mm范围内变动时,不仅能保证熔覆层无任何柱节结构,且基体和NiWC25结合宽度与熔覆层最大宽度比值恒等于1,从而使基体与NiWC25合金具有良好的冶金结合性能。

Effects of Specific Powder and Specific Energy on the Characteristics of NiWC25 by Laser Cladding

The work aims to investigate the effects law of specific powder and specific energy on the bonding characteristics of alloy powder and matrix, the macroscopic and microstructure of cladding layer, the maximum width of cladding layer and the ratio of bonding width during the laser cladding and then to find the optional range of specific powder and specific energy for cladding layer with column-free structure and good metallurgical junction. A series of single-pass cladding layers were prepared by orthogonal experiments and single control variables. The influence characteristics of the specific powder and specific energy of cladding layer on the column structure, critical combination structure and uniform cylindrical structure were analyzed. When the specific powder of laser cladding was more than 7 vs/mm and the specific energy was more than 200 ws/mm, the ratio of the maximum width to the bonding width of the cladding layer was bigger than 1.41. The gap between the cladding layer and the matrix made the molten alloy powder collapse along the direction perpendicular to the substrate during the cladding process and form a cladding layer with a distinct column structure. When the specific energy was 200 ws/mm and the specific powder was less than 5 vs/mm, the macroscopic morphology of the cladding layer was uniform and appeared cylindrical structure and the ratio of the cladding laser maximum width to the combined width of the substrate and NiWC25 was 1. When the specific powder was larger than 7 vs/mm and the specific energy was less than 100 ws/mm, the NiWC25 and the matrix exhibited a critical cladding layer, and even a matrix and melting NiWC25 alloy powder detachment phenomenon. As long as the specific powder of laser cladding is more than 3~5 vs/mm and the specific energy is within the range of 100~200 ws/mm, it can not only ensure that the cladding layer has no column structure, but also the ratio of the maximum width to the cladding layer is always equal to 1, so as to ensure good metallurgical bonding properties between the matrix and the NiWC25 alloy.