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| Influence of vacuum sintering temperature on microstructure and properties of austenitic stainless steel containing Sn |
| QIN Qun，LIU Xinyu，WANG Tianguo |
| （School of Material Science and Engineering, Hubei University of Automotive Technology, Shiyan 442002, China） |
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Abstract Vacuum sintering makes it easier to expel gas from the pores of stainless steel powder compacts, there‐
by improving the density of stainless steel sintered materials. The sintering process has a significant effect on the
density mechanical properties, corrosion resistance, and other properties of powder metallurgy 304 austenite. This
article uses vacuum sintering to prepare powder metallurgy 304 austenitic stainless steel, and adds a certain
amount of sintering additive Sn to study the effect of vacuum sintering temperature on the microstructure and
properties of 304 stainless steel. The results show that when the sintering temperature is below 1 270 ℃, the
activity of atoms is insufficient, the diffusion degree is weak, and there are many internal pores in the sintered
body, with irregular and uneven distribution of pores and low density. When the sintering temperature is
1 270 ℃, the number of pores in the microstructure of the sample is relatively small, the pore size is small, and
the shape is more regular. At this sintering temperature, the dimples in the fracture surface of the sample are deep
and uniformly distributed, and the dimples are connected in a network form. The number of pores is small, and
the distribution is uniform, with a tendency to spheroidize. When the sintering temperature is 1 270 ℃, the activi‐
ty of atoms increases. Due to the addition of sintering additive Sn, a certain amount of liquid phase appears dur‐
ing the sintering process. Under the surface tension of the liquid phase, the diffusion speed of metal atoms accel‐
erates, and solid particles are rearranged to achieve dense arrangement. This causes the pores generated in the sin‐
tered body to be filled by the liquid phase, reducing the number of pores in the sintered body, and significantly increasing the density of sintered stainless steel. The hardness and tensile strength reached their maximum values,
which were 7.31 g/cm3, 62.23HRB, and 363.34 MPa, respectively. When the sintering temperature exceeds 1
270 ℃, the number of pores in the microstructure of the sintered sample increases, the size of the pores increas‐
es, and the density, hardness, and tensile strength of the sintered sample decrease. When the sintering temperature
is 1 270 ℃, the self corrosion current of 304 stainless steel sintered sample is the smallest and has the best corro‐
sion resistance performance. As the sintering temperature increases, the corrosion current density of the sample
decreases, and the corrosion resistance of the sample improves. The main reason is that as the sintering tempera‐
ture increases, a higher sintering temperature is conducive to the diffusion of atoms and the generation of liquid
phase. The porosity of the sample decreases, the density increases, and the corrosion resistance of the sample is
improved. The appropriate sintering temperature increases the liquid phase in the sintered body of 304 stainless
steel, fully metallurgical bonding between particles, reduces the number and size of pores, and improves the alloy‐
ing degree of the sintered sample, which is conducive to the densification of the 304 stainless steel sintered sam‐
ple, and improves the mechanical properties and corrosion resistance of the sample.
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Received: 10 January 2023
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Corresponding Authors:
王天国（1978—），男，博士，教授，主要研究方向为粉末冶金材料制备技术。
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2023, Vol. 33 
