利用超高速激光熔覆(ultra-high speed laser cladding,UHSLC)技术在42CrMo钢基体表面制备了 M2高速钢涂层.采用扫描电子显微镜(scanning electron microscopy,SEM)、电子背散射衍射(electron backscatter diffraction,EBSD)、能谱仪(energy dispersive spectrometer,EDS)、X 射线衍射仪(X-ray diffraction,XRD)和透射电子显微镜(transmission electron microscopy,TEM)对M2涂层的微观组织结构进行了研究.结合原子力显微镜(atomic force microscopy,AFM)对纳米玻氏压痕的投影接触面积进行了测量和修正计算,并获得了 M2涂层沿截面厚度方向的残余应力分布.结果表明,UHSLC制备的M2涂层稀释率较低,与42CrMo钢基体形成了宽度约为1～2 pm的熔覆界面,界面冶金结合良好.靠近熔覆界面的M2组织形貌以等轴状为主,中间区呈现大量片状马氏体组织,浅表区由晶内纳米级针状马氏体+晶界"篮网"状晶界碳化物组成."篮网"状碳化物主要为非稳态V4C3和非稳态Cr3(W10C3)2,且相互符合[(5)(15)3]v4C3||[110]Cr3(W10C3)2和(015)v4C3||((1)15)Cr,(W10C3)2的平行位相关系.修正计算了 pile-up引入的压头接触投影面积,所获得的M2熔覆界面残余应力信息与G&S(Giannakopoulos & Suresh)能量法吻合度较高.当M2熔覆界面位置的残余拉应力达到约300 MPa的峰值后,在42CrMo钢热影响区内呈现应力陡降并随后进入压应力状态.
Microstructure and interfacial stress of M2 coating prepared by UHSLC
The M2 HSS coating was prepared on the surface of 42CrMo steel substrate using ultra-high speed laser cladding(UHSLC).The microstructure and characteristics of the M2 coating were investigated by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),energy dispersive spectrometer(EDS),X-ray diffraction(XRD)and transmission electron microscopy(TEM).The projected contact area of Bohrer-nanoindentation was measured and corrected to calculate in combination with atomic force microscopy(AFM),and the residual stress distribution of the M2 coating in the direction of thickness was obtained.The results showed that the M2 coating prepared by UHSLC had a low dilution rate and formed a cladding interface with a width of about 1～2 pm,and the interface metallurgy was well bonded.The M2 microstructure near the interface was predominantly equiaxial,with a large amount of lamellar martensite in the intermediate zone,and the subsurface zone consisted of intracrystalline nanoscale acicular martensite+grain boundary"basket net"-like carbides.The"basket net"-like carbides were composed of unstable V4C3 and unstable Cr3(W10C3)2,in accordance with parallel orientation relationships of[(5)(15)3]v4C3||[110]Cr3(W10C3)2and(015)v4C3||((1)15)Cr3(W10C3)2.The projected contact area of Bohrer-nanoindentation introduced by pile-up was corrected and the obtained information on residual stresses at the M2 cladding interface was in good agreement with the G&S(Giannakopoulos & Suresh)energy method.After the residual tensile stress near the M2 cladding interface reached a peak value of about 300 MPa,it showed a steep decrease in stress within the heat affected zone(HAZ)of the 42CrMo steel and subsequently entered the compressive stress state.
万方数据
维普
