Si,Al对激光熔覆MoFeCrTiW高熵合金涂层组织性能的影响

为了提高材料表面的耐磨性和高温抗氧化性,利用激光熔覆技术在Q235钢表面制备了MoFeCrTiW高熵合金涂层,并采用X射线衍射仪(XRD)、扫描电镜(SEM)和磨损试验机等研究了Si,Al添加对高熵合金涂层组织、相结构、耐磨性和高温抗氧化性能的影响。结果表明:激光熔覆MoFeCrTiW高熵合金涂层组织为等轴晶,单独添加等物质的量的Si或Al时,涂层分别为共晶组织或树枝晶,同时添加等物质的量的Si和Al时,涂层组织为细小的等轴晶。各高熵合金涂层的主体相均为BCC相,随着Si,Al的添加,BCC相的晶格常数减小。添加等物质的量的Al有助于抑制涂层中金属间化合物的形成,使涂层耐磨性降低;添加等物质的量的Si则会形成含Si的金属间化合物和一些未知相,提高涂层耐磨性。激光熔覆MoFeCrTiW高熵合金涂层在800℃的抗氧化性较高,Si、Al的添加可使涂层的高温抗氧化性进一步提高。

Effect of silicon and aluminum on microstructure and properties of laser cladding MoFeCrTiW high-entropy alloy coating

In order to improve the wear resistance and high-temperature oxidation resistance of materials surface, MoFeCrTiW high-entropy alloy coating, named MoFeCrTiW HEA coating, was fabricated on Q235 steel by laser cladding. The effect of silicon and aluminum on the microstructure, phase, wear resistance and high-temperature oxidation resistance were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and wear tester. The results show that the microstructure of MoFeCrTiW HEA cladding coating is composed of equiaxed grains. After adding equimolar silicon or aluminum respectively, the microstructure of coating is eutectic or dendrites. The microstructure consists of fine equiaxed grains when adding equimolar silicon and aluminum simultaneously. The main phase of HEA coatings is BCC structure. With the addition of silicon and aluminum, the lattice constants of BCC are reduced. Adding equimolar aluminum can contribute to restrain the formation of intermetallic compound and decrease the wear resistance of coatings, whereas adding equimolar silicon can promote the formation of intermetallic compound and some unknown phases, then the wear resistance of coatings can be increased. MoFeCrTiW HEA cladding coating exhibits high oxidation resistance at 800 ℃, the high temperature oxidation of coatings can be further increased after adding silicon and aluminum.