激光3D打印方法制备Nb/SiC体系梯度材料的微观组织及反应机理

Microstructure of Nb/SiC system gradient material fabricated by laser 3D printing method and reaction mechanism

采用激光3D打印的方法制备了Nb/SiC体系梯度材料,获得了从纯金属铌逐渐过渡到40%Nb+60%SiC(体积分数)复合层的梯度材料.通过扫描电子显微镜(SEM)、电子探针(EPMA)和X射线衍射仪(XRD)分析了梯度复合层的微观组织.结果表明,层与层之间结合良好,激光熔敷过程中铌和SiC之间发生了反应,生成了Nb_5Si_3,Nb_2C,NbC和NbSi_2等二元化合物,并且随着SiC含量的逐渐增加,梯度材料内部产物呈现如下变化趋势:Nb+Nb5Si_3+Nb_2C+NbC→Nb_5Si_3+NbSi_2+SiC+NbC→NbSi_2+SiC+NbC.当SiC含量达到30%时,梯度复合层中残留金属铌消失,且开始出现残余的SiC颗粒,随着原始SiC比例的增加,复合层中不仅残余SiC的含量增加,而且粒度也逐渐增大.

Nb / SiC system gradient material was fabricated by laser 3D printing method. The Nb / SiC sample with composition changing from pure Nb to 60% SiC( volume fraction) was prepared. The microstructure of gradient material was analyzed with scanning electron microscope( SEM) and electro-probe microanalyzer( EPMA),and X-ray diffraction( XRD) spectrometer was used for determination of the formed phases in graded layers. It was found that chemical reaction took place between Nb and SiC in the gradient layers during laser melting process,and the reaction products included Nb_5Si_3,Nb_2C,NbC and NbSi_2. With increasing of SiC content,the products of gradient material changed as follows: Nb + Nb_5Si_3+ Nb_2C + NbC → Nb_5Si_3+ NbSi_2+ SiC + NbC →NbSi_2+ SiC + NbC. Residual SiC particles began to appear when the SiC content reached 30%,and residual SiC content and its size in the material gradually increased with the increase of SiC ratio.