| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 92 === Traditional powder metallurgy (P/M) process can produce economically net-shape mechanical or structural parts in quantity. To improve the competitiveness of P/M parts, this study investigates the influence of atmosphere, sintering temperature, alloying element, carbon content , and tempering temperature on the mechanical properties of diffusion-bonded steel powders.
The results show that 91%N2+9%H2 atmosphere, 1250℃ sintering temperature, and adding 316L stainless steel powder will improve the mechanical properties of sintered parts. Increasing the carbon content from 0.6wt% to 0.8wt% is not helpful. Adding 316L stainless steel powder decrease slightly the carbon content of sintered parts and the heat-treated mechanical properties. Increasing tempering temperature from 180℃ to 230℃ can effectively increase the heat-treated mechanical properties.
This study also investigates the microfracture behavior of sintered parts using an in-situ tensile test. It was found that the microcrack initiates at the Ni-rich ferrite grain boundary near the neck region and propagate easily along the boundary. The microstructure around pores and the heterogeneous structure can effectively delay crack nucleation and propagation and thus improve the mechanical properties of sintered parts.
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