机械振动辅助激光熔覆Fe-Cr-Si-B-C涂层的显微组织及界面分布形态

采用机械振动辅助激光熔覆复合改性新工艺,在45钢表面制备了单道Fe-Cr-Si-B-C合金涂层。借助X射线衍射(XRD)、扫描电镜(SEM)和能量分散谱(EDS)分析了熔覆层的物相组成、微观结构和元素分布,通过HVS-1000型显微硬度计测试了熔覆层的显微硬度。结果表明,熔覆层主要由α-(Fe,Cr)固溶体、M7C3(M=Fe、Cr)碳化物、Fe2B硼化物和少量Fe0.9Si0.1组成。在机械振动辅助作用下,熔覆层结合界面组织由平面晶向带状和柱状晶转变,振幅为0.13~0.18mm时的晶粒细化效果最为明显;熔覆层中增强相形态随着频率的增加由短杆状向颗粒状、层状、条状转变,分布形态由杂乱分布向弥散分布和网状分布转变。相比未加机械振动的熔覆层,机械振动下的熔覆层中气孔、裂纹减少,显微硬度提高了约13.9%。这些结果显示熔覆层中显微组织形态及其分布主要受振幅和频率协同作用的影响。

Microstructure and interface distribution of Fe-Cr-Si-B-C laser cladding alloy coatings assisted by mechanical vibration

Fe-Cr-Si-B-C alloy coatings were fabricated on 45 medium carbon steel by combination of a laser cladding and a mechanical vibration surface modification process. The microstructures, element distributions, phase compositions and microhardnesses of the Fe-Cr-Si-B-C cladding coatings were investigated by the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Disperse Spectroscopy (EDS) and the HVS-1000 hardness tester. The results show that the cladding coatings are mainly composed of α-(Fe, Cr)solid solution, M₇C₃(M=Fe, Cr)carbide, Fe₂B boride and a small amount of Fe_0.9Si_0.1 compound. The microstructure of cladding coating interface transforms from a plane crystal to a banded structure and a columnar crystal under the mechanical vibration condition, and the grain refinement effect is the most obviousy when the amplitude is 0.13-0.18 mm. Moreover, the enhanced phases in cladding coatings transform from the short rod to granular, lamellar and banded structures with the increase of vibration frequency, and the distribution patterns change from random distribution to dispersed and network distributions. Compared with the normal laser cladding coating, more less pores and cracks exist in the cladding coating under mechanical vibration condition, and the maximum microhardness increases by 13.9%. These results mean that the microstructures and distributions in the cladding coatings are influenced by a synergetic mechanism of amplitude and frequency.