摘要
目的 提高60Si2Mn钢的表面耐磨损性能.方法 采用同步送粉方式在60Si2Mn钢表面进行激光熔覆X1、X22种铁基粉末.通过金相显微镜、场发射扫描电镜和X射线衍射仪,观察和分析熔覆层的显微组织、化学元素分布及相组成,采用显微硬度仪、多功能摩擦磨损试验机进行硬度、耐磨损性能测试.结果 2种熔覆层均无裂纹、气孔等缺陷,涂层内部存在大量树枝晶、等轴晶和少量沿基材表面生长的平面晶,其中X1熔覆层的顶部区域等轴晶数量较多,组织更细小均匀.2种熔覆层均由相同物相(α-Fe)固溶体组成,未出现明显的其他物相的衍射峰.基体60Si2Mn钢平均硬度约为300HV,X1熔覆层的硬度为950～1 000HV,平均硬度为975HV.X2熔覆层的硬度为784～821HV,平均硬度为803HV.经过球-盘磨损试验后,X1、X2熔覆层以及基体的体积磨损率分别为1.32×10-4、1.94×10-4、3.29×10-4 mm3/(N,m).结论 2种熔覆层的硬度和耐磨损性能均优于基体,其中X1熔覆层的平均硬度比X2熔覆层的高约21％,其体积磨损率最小,耐磨损性能更好.
Abstract
As an advanced surface strengthening and repairing technology,laser cladding is used to prepare metallurgically bonded coatings,which has the advantages of high surface quality,low dilution rate,small heat-affected zone in the base material,and low material loss.It has been widely utilized in many fields,such as agricultural machinery,aerospace,high-speed trains,railways,and mining machinery.In this study,laser cladding technology was employed to deposit two types of iron-based coatings on the surface of 60Si2Mn steel,which was commonly used as rotary tiller blade material.The microstructure,phase structure,hardness in the bonding zone,and wear resistance of the two cladding coatings were analyzed in detail.Both types of cladding coatings exhibited no cracks,pores,or other defects.They contained a significant number of dendritic crystals,equiaxed crystals,and a small number of planar crystals growing along the substrate surface.The different microstructures of the cladding coatings were related to the constitutional supercooling during the solidification process,which was primarily affected by the ratio of the temperature gradient(G)to the solidification rate(R).At the interface between the cladding coatings and the substrate,solidification firstly occurred with the largest temperature gradient and the slowest solidification rate.In this region,there was no significant constitutional supercooling,leading to the formation of a planar crystalline structure.As the solidification process continued,the temperature gradient decreased and the solidification rate increased.This resulted in a larger constitutional supercooling and interface instability.The microstructure changed from planar crystals to a mixture of columnar and dendritic crystals.When the solid-liquid interface approached the surface of the cladding coatings,the cooling rate was accelerated,corresponding to a smaller G/R.At this stage,the nucleation rate exceeded the growth rate of the grains,leading to the transformation of the micro structure into smaller equiaxed crystals.The X1 cladding coating had a higher quantity of equiaxed crystals on the surface,with a finer and more uniform microstructure.This was attributed to the presence of the vanadium(V)element in X1 powder,which could refine the grain structure and microstructure.Both types of cladding coatings exhibited diffraction peaks at the same angles(44.7°,65.0°,82.3°),indicating that they were composed of the same(α-Fe)solid solution.Both types of cladding coatings exhibited higher hardness and wear resistance compared to the substrate.The substrate had an average hardness of approximately 300HV,while the X1 cladding coating had a hardness of 950-1 000HV with an average hardness of 975HV and the X2 cladding coating had a hardness of 784-821HV,with an average hardness of 803HV.The X1 cladding coating had an average hardness approximately 21％higher than the X2 cladding coating.The volume wear rates provided information about the wear resistance of the coatings.X1 cladding coating exhibited the lowest volume wear rate among the three materials,with a value of 1.32×10-4 mm3/(N·m).X2 cladding coating had a slightly higher volume wear rate of 1.94×10-4 mm3/(N·m),while the substrate material had the highest wear rate of 3.29×10 4 mm3/(N·m).Therefore,the X1 cladding coating shows the best wear resistance,indicating that it is more resistant to material loss or damage under sliding or abrasive conditions.
基金项目
2021年产业基础再造和制造业高质量发展专项项目(TC210H02X-04)
金属材料磨损控制与成型技术国家地方联合工程研究中心2021年开放课题(HKDNM202104)
国家科技期刊平台
NSTL
万方数据