激光包覆焊接制备复合层研究

发布时间：2018-05-26 00:14

本文选题：激光焊接 + 304不锈钢　；参考：《中国矿业大学》2017年硕士论文

【摘要】：立柱是液压支架设备中的易损件,煤矿严重的腐蚀环境直接影响着立柱的使用寿命,容易出现磨损、腐蚀、变形等现象,从而导致液压系统失效,因此,要对立柱表面进行处理。传统的表面处理方法为电镀、化学镀和激光熔覆,前者容易产生含重金属离子的电镀废水和各类酸雾废气,污染严重,后者使用的熔覆合金粉末制作成本高、周期长,且增加空气中会悬浮颗粒物,本文首次提出用激光包覆焊接代替激光熔覆,以薄板带材代替粉末,对立柱表面进行处理。本文首先以304不锈钢和27SiMn钢为研究对象,对其进行单道激光搭接焊和激光包覆焊,通过光学显微镜、扫描电镜、X射线衍射分析仪、磨损试验机以及电化学测试站,研究焊缝的凝固模式、工艺参数对焊缝形貌的影响以及所制备焊接复合层的耐磨性和耐腐蚀性,然后再以Inconel 718合金代替304不锈钢进行包覆焊制备复合层,对比两种复合层的耐磨性和耐腐蚀性。研究结果如下:304不锈钢焊缝的边缘为柱状晶,中心为等轴晶,室温下的组织为铁素体和奥氏体;27SiMn钢焊缝的中心组织以板条状的马氏体为主,热影响区组织为马氏体和贝氏体;两种材料进行搭接焊时,获得了良好的冶金结合,焊缝过渡区组织为马氏体、铁素体和奥氏体,304不锈钢母材的平均显微硬度约为178.1 HV,焊缝的平均硬度为279.4 HV,27SiMn钢母材的平均显微硬度约为260.1 HV,焊缝的平均显微硬度约为392.9 HV。不同工艺参数均能获得平整、光滑、致密的焊缝。随着激光功率的增加,焊缝的熔深、熔宽以及硬度值均增大;随着焊接速度的增加,焊缝的熔深、熔宽减小,焊接速度的变化对焊缝的硬度影响不大;焊缝熔深和硬度均随离焦量的变化先增加后减小,而对熔宽的影响较小,各工艺参数下焊缝的束腰高和束腰宽均变化不大。在不同的激光功率、焊接速度、离焦量以及搭接率下,均能获得成形良好的304不锈钢/27SiMn钢复合层;在激光功率400 W、焊接速度0.8 m/min、离焦量0 mm以及搭接60%的工艺参数下,复合层的磨损量最小;对304不锈钢/27SiMn钢复合层进行电化学测试并与304不锈钢母材进行比较,复合层的耐腐蚀性略差于304不锈钢母材。对Inconel 718合金和27SiMn钢进行激光包覆焊制备复合层,其表面硬度值是304不锈钢/27SiMn钢复合层的1.74倍,磨损量也仅为304不锈钢/27SiMn钢焊复合层的65%,但耐腐蚀性能略差于304不锈钢/27SiMn钢复合层。
[Abstract]:The pillar is the easily damaged part in the hydraulic support equipment, the serious corrosion environment of the coal mine directly affects the service life of the pillar, easy to appear the phenomenon such as wear, corrosion, deformation and so on, thus causes the hydraulic system to fail, therefore, The surface of the column should be treated. The traditional surface treatment methods are electroplating, electroless plating and laser cladding. The former can easily produce electroplating wastewater containing heavy metal ions and all kinds of acid mist exhaust gas. In this paper, laser cladding welding instead of laser cladding and thin strip instead of powder are proposed to treat the surface of column. In this paper, 304 stainless steel and 27SiMn steel were first studied, and the single pass laser lap welding and laser cladding welding were carried out. By means of optical microscope, scanning electron microscope (SEM), X-ray diffraction analyzer, wear tester and electrochemical test station. The solidification mode of weld, the influence of process parameters on weld morphology and the wear resistance and corrosion resistance of the welded composite layer were studied. Then, the composite layer was prepared by coating and welding with Inconel 718 alloy instead of 304 stainless steel. The wear resistance and corrosion resistance of the two kinds of composite layers are compared. The results are as follows: the edge of the weld is columnar and the center is equiaxed. At room temperature, the microstructure of the weld is mainly composed of lath martensite and martensite at room temperature, and the microstructure of the heat-affected zone is martensite and bainite. Good metallurgical bonding was obtained in the lap welding of the two materials, and the microstructure of the transition zone of the weld was martensite. The average microhardness of ferrite and austenitic stainless steel is about 178.1 HV. the average hardness of weld is about 260.1 HV. the average microhardness of weld is about 392.9 HV. Smooth, smooth and compact welds can be obtained with different process parameters. With the increase of laser power, the weld penetration depth, weld width and hardness increase, and with the increase of welding speed, the weld penetration depth and weld width decrease, and the variation of welding speed has little effect on the weld hardness. The weld penetration depth and hardness increased first and then decreased with the change of defocusing amount, but had little effect on the weld width. The composite layer of 304 stainless steel / 27SiMn steel can be obtained with different laser power, welding speed, defocusing amount and lap ratio, and the laser power 400 W, welding speed 0.8 m / min, defocus 0 mm and lap 60% process parameters are obtained, and the results are as follows: (1) when the laser power is 400 W, the welding speed is 0.8 m / min, the defocus is 0 mm, and the lap ratio is 60%. The corrosion resistance of the composite layer was slightly worse than that of 304 stainless steel base metal, and the electrochemical test of 304 stainless steel / 27SiMn composite layer was carried out and compared with 304 stainless steel base metal. The surface hardness of Inconel 718 alloy and 27SiMn steel was 1.74 times of that of 304 stainless steel / 27SiMn steel by laser cladding welding, and the surface hardness of the composite layer was 1.74 times higher than that of 304 stainless steel / 27SiMn steel. The wear rate is only 65% of 304 stainless steel / 27SiMn composite layer, but the corrosion resistance is slightly worse than 304 stainless steel / 27SiMn steel composite layer.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD355.4;TG456.7

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