Effect of NbC Content on Microstructure and Properties of Laser Clad Stainless Steel Coatings
YI Hong1, GUO Wenrong2, GUO Liang2, HUO Fengfeng2, HUI Xiaobin2, LI Xiaofeng1, 3
1. North University of China, Taiyuan 030051, China;
2. Zhiqi Railway Equipment Co., Ltd., Taiyuan 030032, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
In this paper, stainless steel coatings with different NbC contents were prepared on the surface of EA1T axle steel using laser cladding technology. The phase structure and microstructure evolution of the composite coatings were analysed using X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), and the hardness and tribological properties of the coatings were determined. The results show that the addition of NbC plays a role in grain refinement, while Fe (Nb, C) type hard phases are precipitated between the grains. However, the addition of NbC resulted in the disruption of the directionality of the dendrites in the coating, but the coating properties were enhanced and increased with the addition of NbC. In particular, when the mass fraction of NbC is 20%, all of the added NbC melts and then precipitates islands of hard phase between the grains. The hardness and wear resistance of the coating is significantly improved by the fine grain strengthening and diffusion strengthening caused by the NbC addition. The addition of 20% NbC increased the hardness by 15% compared to the uncoated NbC, reaching a maximum hardness of 60HRC; The wear coefficient was significantly reduced to 0.75, with the best reinforcement effect. The wear surface plough furrows of the composite coating with 20% NbC were shallow, and the wear mechanism was abrasive wear.