Influence of SS316L Nanoparticles on the Sintered Properties of Two-Component Micro-Powder Injection Moulded Bimodal SS316L/Zirconia Bi-Materials

Two-component micro-powder injection moulding (2C-μPIM) is a prospective approach for fabricating bi-material micro-components of stainless steel 316L (SS316L) and 3 mol% yttria-stabilised zirconia (3YSZ) at an appealing cost. However, the fundamental challenge lies in preventing the formation of large-scale cracks at the interface of two different materials during sintering. This study investigated how SS316L nanoparticles in bimodally configured SS316L powder that incorporated both nanoparticles and microparticles influenced the sintering of 2C-μPIM-processed miniature bi-materials made of bimodal SS316L and 3YSZ. In this study, feedstocks were developed by integrating monomodal (micro-sized) SS316L powder, three types of nano/micro-bimodal SS316L powders, and 3YSZ powder individually with palm stearin and low-density polyethylene binders. The results indicated that increasing the SS316L nanoparticle content to 45 vol.% caused a 19.5% increase in the critical powder loading in the bimodal SS316L powder as compared to that in the monomodal SS316L powder. The addition of SS316L nanoparticles increased the relative density and hardness of the sintered bi-materials, with the maximum values obtained being 96.8% and 1156.8 HV, respectively. Field emission scanning electron microscopy investigations revealed that adding 15 vol.% and 30 vol.% SS316L nanoparticle contents reduced interface cracks in bi-materials significantly, while 45 vol.% resulted in a crack-free interface.