스테인리스 스틸 316L 바이모달 분말의 압축성형 및 소결 거동 분석

Abstract

Powder size is one of the critical factors for successful manufacturing in powder metallurgy. The component fabricated by the nano sized powder has higher mechanical properties when compared to a component fabricated by micro sized powder. In this study, a bimodal powder mixed with different sizes of powder has been analyzed to overcome this drawback of using of mono sized or narrow size distribution of powders. It is expected that the fractional packing density will be maximum for a certain ratio of the small and large particles. In this research effects of nano powder in bimodal powder mixture are studied. Bimodal powder was prepared with 100 nano meter and 4 micro meter sized stainless steel 316L powder. They were mixed into 5 grades that differ in nano powder volume ratio from 0 to 100 percent. Prepared powder’s characteristics were verified with tap density, BET surface, particle size analyze and pycnometer density. Cylindrical samples were prepared via die-pressing. The dilatometric studies were carried out to analyze the densification during sintering. Effects of vol.% of nano powders on sintering behavior were verified. These experiments are carried out as an advanced research for powder injection molding of bimodal powder. So, basic experiments of powder injection molding were conducted. Firstly, mixed bimodal powder that mixture of micro and nano powder was premixed by turbular mixer. To verify the optimum ratio of binder and powder, torque rheometer experiments were carried out before making feedstock that is the mixture of binder system and powder. And then Feedstocks were fabricated by twin extruder mixer and mixture homogeneity was evaluated through rheometer experiments.