H13钢表面电火花沉积Nb涂层组织与性能研究

Microstructures and Properties of Niobium Coating on H13 Steel Substrate by Electrospark Deposition

目的提高H13钢表面的力学性能和耐蚀性,延长模具的使用寿命。方法用Nb棒作为电极,氩气作为保护气体,通过电火花沉积技术在H13钢表面制备Nb沉积层。利用扫描电子显微镜分析沉积层的表面形貌、显微结构及磨痕形貌,利用X射线衍射仪分析沉积层的相组成,利用能谱仪分析沉积层的元素分布,采用显微硬度计和磨损试验机测试沉积层的显微硬度和耐磨性,采用电化学工作站对沉积层进行耐蚀性测试。结果 Nb电火花沉积层表面呈橘皮状,具有一定的粗糙度,主要由Fe_2Nb和Fe_(0.2)Nb_(0.8)等相组成。沉积层截面组织连续、致密,无明显缺陷,强化层内存在大量的微晶组织和非晶组织。Nb涂层与基体发生了元素的相互扩散和冶金结合的过程。沉积层显微硬度高达642HV,为基体的3.2倍。在同等磨损条件下,Nb沉积层磨损失重约为基体的1/3,磨痕较浅。沉积层在3.5%NaCl溶液中的电化学自腐蚀电位比基体提高了113 mV,自腐蚀电流密度显著降低。结论在H13钢表面电火花沉积Nb涂层,可有效提高其表面的显微硬度、耐磨性和耐蚀性,从而延长模具的使用寿命。

The work aims to improve the mechanical properties and corrosion resistance of H13 steel surface,so as to extend the service life of mould.Niobium deposited coating was prepared on H13 steel substrate by electrospark deposition process with niobium electrode as coating material and argon as shielding gas.Surface morphologies,microstructures and wear morphologies of the deposited coating were analyzed by scanning electron microscope(SEM).Phase composition and elements distribution of the coating were tested by X-ray diffractometer(XRD)and energy disperse spectroscopy(EDS).Microhardness and wear resistance of the coating were measured by microhardness tester and wear tester.Corrosion resistance of the coating was determined by electrochemical workstation.The surface of niobium deposited coating mainly consisted of Fe2Nb and Fe0.2Nb0.8 looked like the surface of orange and had certain roughness.The microstructure of the coating cross section was continuous and dense without obvious defects.The strengthening coating contained plenty of microcrystalline structures and amorphous structures.The diffusion of chemical elements occurred between the niobium coating and the H13 steel substrate.The microhardness of the coating was 642HV,which was about 3.2 times higher than that of the H13 steel substrate.The wear mass loss of niobium coating was about one third of the H13 substrate in the equal wear conditions and the wear scar was shallow.The electrochemical self-corrosion potential of the coating in 3.5wt.%NaCl solution was improved by about 113 mV compared with the substrate,while the electrochemical self-corrosion current density was decreased obviously.Nb coating deposited on H13 steel substrate by electrospark can effectively improve microhardness,wear resistance and corrosion resistance of the H13 steel and extend the service life of the mould.