利用激光熔覆技术,在6063Al表面制备了添加有不同含量La2O3的Ni60合金熔覆层,并通过金相显微镜、X射线衍射仪(XRD)、扫描电镜(SEM)和能谱仪(EDS)等设备进行了测试分析,研究La2O3含量对铝合金表面激光熔覆Ni基熔覆层组织、相结构、成分等微观结构的影响。结果表明:当合金中稀土La2O3含量高于5%(质量分数,下同)时熔覆层易出现气孔,低于2%时易出现熔覆层开裂、与基体结合不良等缺陷,加入5%的稀土氧化物La2O3可有效地减少熔覆层中的裂纹、孔洞;不同La2O3含量的熔覆层主要相结构均为β-NiAl(Cr)和少量的Al3Ni、AlNi3、Al等,添加稀土以后XRD图中出现了微量的稀土化合物La2O3、Al4La,且NiAl相的(100)有序峰几乎消失,晶粒取向偏向于(110)、(200)和(211),而(110)有序峰出现不同程度的偏移;添加5%La2O3的熔覆层比不添加稀土的Ni60熔覆层元素分布均匀,稀释率更低,组织中孔隙率大幅降低,晶粒度变大且细化作用明显;熔覆层主要成分为NiAl-Cr共晶组织,稀土元素偏聚在晶界位置并形成了稳定的Al4La等稀土化合物。
Ni-Based alloy coatings with different contends of rare-earth La2O3 are prepared on the surface of 6063 aluminum alloy by using laser cladding.The effects of rare earth La2O3 on microstructure,phase structure and composition of laser cladding Ni-Based alloy coatings on6063 Al alloys are investigated by means of optical microscope(OM),X-ray diffractometer(XRD),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The results show that with increasing the amount of La2O3(above 5%),the cladding layer tends to form gasholes.When the amount of La2O3 is in the range of 0% ~2% the same below,the cladding layer tends to form cracks,and coating can′t bind tightly with the matrix.Gas-holes and cracks in the coatings reduced with the addition of 5% La2O3.The main phase structures of Ni-based alloy coatings with different contends of rare-earth La2O3areβ-NiAl(Cr)and a small amount of Al3 Ni,AlNi3,Al,etc.After adding rare earth,a little of rare earth compounds La2O3、Al4La is found in XRD diagrams,and NiAl phase(100)crystallographic orientation peak almost disappeared,grain orientation towards(110),(200)and(211),and(110)crystallographic orientation peaks appear different degrees of migration;Compared with Ni60 cladding layer without adding rare earth,Ni60 cladding layer with 5% of rare-earth La2O3 has a uniform element distribution,a lower dilution rate,which significantly reduce the porosity andrefine the grain size;The cladding layer mainly composed of NiAl-Cr eutectic structure,rare earth elements segregate at the grain boundary and form some stable rare earth compound such as Al4 La.