粉芯丝材TIG堆焊原位合成TiC-TiB_2铁基涂层的微观组织研究

Study on Microstructure of In-situ Synthesized TiC-TiB_2/Fe Matrix Coating by TIG Arc/ cored-wires Weld Overlaying

采用TIG弧熔化粉芯丝材堆焊原位合成技术,在20钢基体表面制备出Ti C-Ti B2铁基复合涂层。利用扫描电镜、X射线衍射仪研究堆焊层显微组织,并分析堆焊涂层中Ti C、Ti B2颗粒形成机制。结果表明:堆焊层组织致密无裂纹、气孔等缺陷,与基体呈冶金结合;堆焊层中Ti C颗粒、Ti B2颗粒及Ti B2包覆Ti C的复合颗粒弥散分布在Fe基体上,且从堆焊层结合处至表层,呈现颗粒尺寸由小变大,颗粒浓度增大的特征。Ti C、Ti B2颗粒及Ti B2包覆Ti C的复合颗粒形成机制为液态扩散形核、液固扩散形核并长大。

TiC-TiB2/ Fe matrix composite coating was in-situ synthesized on the surface of 20 steel substrate by TIG/cored-wire weld overlaying. The microstructure of weld overlay coating and formation mechanism of TiB2, TiC and composite particulate of TiB2 cladding TiC in weld overlay coating were investigated using SEM and XRD. The results show that the weld overlay coating presentes a dense microstructure with defect-free of pore and crack, and better metallurgical bond with the substrate; TiC, TiB2 and composite particulate distribute dispersively in Fe matrix of the weld overlay coatings, and froms weld interface to coating surface, the coating is featured with particle size growing bigger and the particle concentration increasing. The formation mechanism of nucleation and growth of TiC, TiB2 and composite particulate is proposed via liquid diffusion and liquid-solid diffusion.