激光熔覆MoFeCrTiWSi_x多主元合金涂层组织和性能研究

Microstructure and Properties of Laser Cladding MoFeCrTiWSi_x Multi-Principal Element Alloy Coatings

在Q235钢表面激光熔覆制备了MoFeCrTiWSi_x(x=0,0.2,0.4,0.6,0.8,1.0)多主元合金涂层,采用X射线衍射仪(XRD)、扫描电镜(SEM)和硬度计等系统研究了Si对涂层的组织、相结构、显微硬度及高温抗氧化性能的影响。结果表明:激光熔覆MoFeCrTiW多主元合金涂层为简单bcc结构,组织为等轴晶。添加Si后,涂层主体相仍为bcc结构,当x≥0.4后,会有少量金属间化合物生成,合金涂层由先共晶bcc相和共晶组织(bcc相+Cr5Fe50Mo8.9Si5.2Ti20.4相)组成,随着Si量的增加,先共晶相的形态由胞状树枝晶转变为柱状树枝晶和等轴树枝晶,共晶组织逐渐增多。涂层从表面至结合区的混合熵呈高熵-中熵变化。涂层硬度和900℃时的抗氧化性能随着Si含量的增加有所提高,当x=1时,涂层平均硬度及抗氧化性能最高。

MoFeCrTiWSix（x=0,0.2,0.4,0.6,0.8,1.0） multi-principal element alloy coatings were fabricated on Q235 steel by laser cladding.The effect of silicon on the microstructure,phases,microhardness and high-temperature oxidation resistance were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and microhardness tester etc.The results show that the phase of laser cladding Mo Fe Cr Ti W multi-principal element alloy coating is single bcc structure and its microstructure is equiaxed grains.The main phase is still bcc structure after adding different contents of silicon into the coating.When the content of silicon is no less than 0.4 moles,there exists a little intermetallic compound in the coatings;the microstructures of coatings are composed of proeutectic bcc phase and eutectic structure of bcc phase and Cr5Fe50Mo8.9Si5.2Ti20.4 phase.With the content of silicon increasing,the morphology of proeutectic phase changes from cystiform-dendritic to columnar dendrites and equiaxed dendrites,while the content of eutectic structure is increased gradually.From the surface to bonding zone of coatings,the distribution of the mixing entropy changes from high entropy to medium entropy.With the addition of silicon,the microhardness and high-temperature oxidation at 900 °C of coatings are increased.When x is 1.0,both the microhardness and the high-temperature oxidation resistance are the highest.