原位自生ZrC-ZrB2/铁基氩弧熔覆层

In-situ synthesis of Fe-based ZrC-ZrB2 composite coating produced by GTAW

关键词:  氩弧熔覆层  原位自生  显微组织  生长机制

Key words:  GTAW overlay  in-situ synthesis  microstructure  growth mechanism

摘要:

将锆粉、B₄C粉和铁粉预涂在Q235钢表面,利用氩弧熔覆技术成功制备出原位自生ZrC-ZrB₂颗粒增强的铁基复合涂层,利用扫描电镜、X射线衍射仪和能谱仪分析了熔覆层的显微组织,探讨了增强相ZrC-ZrB₂的生长机制,并测试了熔覆层的硬度和室温干滑动磨损条件下的耐磨性能.结果表明,熔覆层由呈针状或棒状分布的ZrCZrB₂复合体和块状或花瓣状的ZrC颗粒组成,增强相的微观形貌与其形核和周围环境密切相关,熔覆层与基体呈良好的冶金结合;熔覆层的维氏硬度可达1 200 MPa,耐磨性为基体的20倍.

Abstract:

A Fe-based composite coating reinforced by ZrC-ZrB₂ particles has been successfully fabricated on Q235 steel by gas tungsten arc welding(GTAW) cladding process utilizing the in situ reaction of pre-placed Zr, B4 C and Fe powders. The microstructure of the coating was analyzed by scanning electron microscopy(SEM), X-ray diffraction(XRD), energy-dispersive spectrum(EDS), and the growth mechanism of the ZrC-ZrB₂ reinforcement was discussed. Meantime, the microhardness and the wear resistance of the composite coating were examined by means of microhardness tester and wear tester at room temperature, respectively. The results show that the coating that has excellent metallurgical bonding with substrate can be obtained. The main phases of coating are ZrC, ZrB₂ and α-Fe, in which the ZrC phase exhibits hexahedron and petalled shapes and the ZrC-ZrB₂ compound presents acicular and rod shape. The microhardness of coating is up to 1 200 MPa, and the wear resistance is about twenty times higher than that of the Q235 steel.