Investigation On Sintering Behaviors Of Porous316L Stainless Steel Fiber Felt

Porous metallic fiber materials (PMFMs) possess many superior properties such as excellent permeability, absorption of electromagnetic waves, good ductility and impact tenacity. PMFMs have been widely used to produce filters, silencers, electromagnetic shielding, catalyst supports, heat exchangers, fuel cells and so on. Sintering is an important step in producing PMFMs. However, research about fiber sintering is still weak. In this paper, the sintering behaviors of316L stainless steel fibers were investigated by using optical microscopy (OM), scanning electron microscopy (SEM), tensile tester, nano indentation and so on. The activation energy and diffusion mechanisms of PMFMs during sintering were firstly reported. Meanwhile, the effect of microwave on the sintering behavior of316L stainless steel fibers was studied. The achievements of this study not only have an important practised meaning on preparing PMFMs which have good performance, but also play a guiding role in establishing the sintering model for PMFMs. The main conclusions of the present dissertation are listed as follows:(1) The grain size, amount of the sintering neck and the relative densities of the fiber felt increase with the increasing of both the sintering temperature and the sintering time.(2) The sintering densification of the fiber felts is dominated by volume diffusion mechanism at lower sintering temperature and relative densities. As more grain boundaries are formed with the increasing of sintering temperature and relative density, the grain boundary diffusion will also contribute to the densification of the specimen.(3) With the increasing of both the sintering temperature and the sintering time, the Strain hardening capacity of316L stainless steel fibers decrease, and the fiber hardness and tensile strength decrease with the grain growth in fibers.(4) Microwave sintering of316L stainless steel fiber felt is feasible, and the suitable sintering temperature and holding time are1200℃and10-20min, respectively. In these schedules, a great amount of sintering necks could be formed in fiber felt and the grain size of fiber skelenton could remain small.(5) Compared with conventional sintering, fiber felt sintered by microwave sintering possesses smaller grains and rather lower values of activation energy. Furthermore, because microwave sintering takes short time and less power. The fiber felt sintered in microwave proceeds more easily, and the microstructure of PMFMs is more uniform.