Q345钢与铝青铜激光熔覆工艺与组织性能研究

发布时间：2018-10-21 14:58

【摘要】：工业的快速发展使得以碳钢、不锈钢、合金钢等为主要材料制造的结构零部件使用的领域越来越广泛,环境越来越复杂,这通常需要材料具有较好的表面性能,例如耐磨耐腐蚀等。铝青铜以其良好的综合力学性能和耐磨损性能越来越多被作为提高结构材料表面性能的覆层材料,但大多是以粉末的形式通过电弧喷涂、等离子喷涂的方式制备涂层,涂层存在结合强度不高,孔隙率大等问题。为了改善这种情况,探索更多覆层制备方法,本课题尝试在Q345钢表面激光熔覆铝青铜丝及铝青铜片,综合运用正交试验法和单因素法研究了激光功率、扫描速度以及电流对铝青铜丝熔覆层宏观形貌及微观组织的影响以及激光功率和扫描速度对铝青铜片覆层微观组织和显微硬度分布规律的影响。运用光学显微镜、SEM、EDS、XRD、全自动显微硬度计等分析了两种铝青铜覆层微观组织及性能,同时研究了载荷、转速、温度、搭接率等不同工艺参数对两种铝青铜覆层摩擦磨损性能的影响,主要研究成果如下:制备的两种铝青铜熔覆层内部均无气孔与裂纹等缺陷,覆层与基体呈冶金结合。在铝青铜丝覆层形貌方面,激光功率对覆层熔深和稀释率影响最明显,扫描速度对覆层熔宽和熔高影响最明显。当搭接率较小时,铝青铜丝覆层主要由大量灰色α相、呈树枝状或点状的黑色κ相以及少量白色γ2相组成;搭接率较大时,覆层主要由大量层片状相间分布的灰色α相、白色γ2相以及少量点状κ相组成。随着搭接率的提高,铝青铜丝覆层硬度先下降再升高,硬度波动幅度逐渐下降,覆层内部微观组织大小以及元素分布逐渐变得均匀,搭接率60%时覆层平均硬度为225HV。与铝青铜丝覆层不同,激光功率密度较小时,铝青铜片覆层主要由β'相与κ相组成;功率密度较大时,覆层主要由γ2相与κ相组成。随着激光功率密度的增加,铝青铜片覆层硬度逐渐降低,且扫描速度对覆层及热影响区的硬度影响更加显著。铝青铜片覆层硬度明显高于铝青铜丝覆层硬度,平均硬度达386HV,且硬度波动幅度较大。对两种铝青铜覆层进行摩擦磨损性能测试,发现随着载荷的增大,两种铝青铜覆层平均摩擦系数逐渐下降,磨痕宽度、磨损量、磨痕线粗糙度逐渐增加。转速对铝青铜覆层平均摩擦系数影响较小,但磨痕宽度、磨损量、磨痕线粗糙度会随着转速的增加而增加,且转速越高,磨痕表面越容易被氧化,黏着磨损和氧化磨损越严重。随着温度的升高,铝青铜丝覆层平均摩擦系数、磨损量、磨痕线粗糙度先增加后减小,磨痕宽度逐渐增加;铝青铜片覆层磨痕宽度和平均摩擦系数逐渐增加,磨损量和磨痕线粗糙度却先下降后逐渐增加。同时,两种铝青铜覆层磨痕氧化程度逐渐增加,黏着磨损和氧化磨损越趋严重,磨粒磨损逐渐减轻。
[Abstract]:With the rapid development of industry, structural parts made of carbon steel, stainless steel, alloy steel and so on are more and more widely used, and the environment is becoming more and more complex, which usually requires better surface properties of materials. Such as wear-resistant corrosion and so on. Aluminum bronze is more and more used as coating material to improve the surface properties of structural materials because of its good comprehensive mechanical properties and wear resistance. However, most of the coatings are prepared by arc spraying and plasma spraying in the form of powder. The coating has some problems such as low bonding strength and large porosity. In order to improve this situation and explore more coating preparation methods, the laser cladding of aluminum bronze wire and aluminum bronze sheet on the surface of Q345 steel was attempted in this paper. The laser power was studied by using orthogonal test and single factor method. The effects of scanning speed and current on the macroscopic morphology and microstructure of aluminum bronze wire cladding and the influence of laser power and scanning speed on the microstructure and microhardness distribution of aluminum bronze laminates were investigated. The microstructure and properties of two kinds of aluminum bronze coatings were analyzed by means of optical microscope and SEM,EDS,XRD, automatic microhardness meter. The effects of different technological parameters such as load, rotation speed, temperature and lap ratio on the friction and wear properties of two kinds of aluminum bronze coatings were studied. The main research results are as follows: there are no defects such as porosity and crack in the two kinds of aluminum bronze cladding coatings, and the coatings are metallurgical bonded with the matrix. In the aspect of the morphology of aluminum bronze wire, laser power has the most obvious influence on the penetration and dilution rate of the coating, and the scanning speed has the most obvious effect on the width and height of the coating. When the overlap ratio is small, the coating of aluminum bronze wire is mainly composed of a large number of grey 伪 phase, black 魏 phase with dendritic or dot shape and a small amount of white 纬 2 phase, and when the overlap ratio is high, the coating mainly consists of a large number of grey 伪 phases distributed between lamellar phases. White 纬 2 phase and a small amount of dot 魏 phase. With the increase of lap ratio, the hardness of aluminum bronze wire cladding decreases first and then increases, and the fluctuation of hardness decreases gradually. The microstructure and the distribution of elements in the coating become more and more uniform. The average hardness of the coating is 225 HV when the lap ratio is 60. Different from the aluminum bronze wire coating, when the laser power density is small, the aluminum bronze sheet coating is mainly composed of 尾 'phase and 魏 phase, and when the power density is high, the coating is mainly composed of 纬 2 phase and 魏 phase. With the increase of laser power density, the hardness of the aluminum bronze coating decreases gradually, and the scanning speed has a more significant effect on the hardness of the coating and the heat-affected zone. The hardness of aluminum bronze sheet coating is obviously higher than that of aluminum bronze wire coating, the average hardness is 386HVand the hardness fluctuates greatly. The friction and wear properties of two kinds of aluminum bronze coatings are tested. It is found that the average friction coefficient of the two kinds of aluminum bronze coatings decreases gradually with the increase of load, and the wear scar width, wear amount and wear line roughness increase gradually. The rotational speed has little effect on the average friction coefficient of the aluminum bronze coating, but the wear scar width, wear amount and wear line roughness will increase with the increase of rotational speed, and the higher the rotational speed, the easier the surface of the wear mark is oxidized, and the more serious the adhesion and oxidation wear is. With the increase of temperature, the average friction coefficient, wear amount and wear line roughness of aluminum bronze wire coating increase first and then decrease, and the wear mark width increases gradually, while the wear mark width and average friction coefficient increase gradually with the increase of temperature. The amount of wear and the roughness of wear line decrease first and then increase gradually. At the same time, the oxidation degree of wear marks of the two kinds of aluminum bronze cladding increases gradually, the adhesion wear and oxidation wear become more serious, and the abrasive wear decreases gradually.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.44

【参考文献】