Preparation And Property Research Of Nanocrystalline High-nitrogen Austenitic Stainless Steel

SUS 304 stainless steel powder and other kinds of alloy powder were mixed. The mixed powder was prepared into samples by mechanical alloying (MA) and Spark Plasma Sintering (SPS) technology. The influence of the ratio of ball to material; milling time; vacuum annealing and adding PCA on particle-degree; grain-degree and particle pattern of the powder was studied in the process of milling. On the other hand, the influence of the sintering temperature and sintering pressure on the density; hardness; grain pattern and corrosion resistant of the sintered samples was studied in process of sintering. At last, the best prepared technics was found. Then the sintered stainless steel samples which are different in nitrogen content were prepared under the best technics. The microstructure and grain pattern of the sintered samples were analysed and the mechanical property and corrosion resistance of different sintered samples were tested. Then nitrogen's influence on the structure and performance of the sintered samples was analysed and the best content of nitrogen to the structure and performance of sintered samples was found.The result of the preparing technics shows that: The particle-degree and grain-degree of powder decrease with the increase of milling time. The increase of the the ratio of ball to material makes the average particle-degree smaller. The vacuum annealing can enhance the austenization of the milled powder. The adding of the PCA can make powder smaller and more uniform. When the sintered temperature is 900℃and sintered pressure is 50 MPa, The hardness and corrosion resistance of sintered sample reach the best. The result of nitrogen's influence on the structure and performance of sample shows that the adding of nitrogen not only makes the grain size of sintered sample smaller, but also makes the structure of sintered sample change from martensite and austenite into single austenite. The test of the performance shows that the hardness; abradability and corrosion resistance of sintered samples are all enhanced with the increase of nitrogen's content, but the tensile strength of sintered sample increases first and then decreases. When nitrogen content is 1.19%, the tensile strength of sintered sample is highest.