粉末冶金多孔高氮奥氏体不锈钢的制备及性能

采用粉末冶金方法制备了多孔高氮奥氏体不锈钢并研究其力学性能和耐腐蚀性能。结果表明，高温气固渗氮能促进双相不锈钢向奥氏体不锈钢的转变，在其显微组织中出现了细条状和颗粒状CrN相析出物。随着造孔剂含量的提高孔隙率随之提高，而力学性能和耐腐蚀性能降低。与普通的多孔不锈钢相比，这种多孔高氮奥氏体不锈钢的力学性能更加优越，源于N的固溶强化和CrN等析出物的强化机制。随着孔隙率的提高多孔高氮奥氏体不锈钢的腐蚀倾向和腐蚀速率逐渐增大，造孔剂含量(质量分数)为10%的试样具有最佳的耐腐蚀性能。提高烧结温度有利于烧结块体的致密化，使腐蚀速率明显下降。

Fabrication and Properties of Powder Metallurgical Porous High Nitrogen Austenitic Stainless Steel

Porous high-N austenitic stainless steel was fabricated via powder metallurgy and its microstructure and properties were investigated. Results show that high temperature nitridation process promotes the phase transformation of the stainless steel from duplex phase to austenitic phase. Precipitations with different morphologies were observed in the microstructure. XRD results and TEM results identified that both the two precipitates with different morphologies are all CrN phase. With the increasing pore-forming agent the porosity of the prepared alloy increased, which could result in degradation of mechanical properties and corrosion resistance. The superior mechanical property of porous alloys fabricated by this method might be ascribed to the effect of solid solution strengthening of the solute N and precipitation strengthening of nitrides. With the increasing porosity, both of the corrosion tendency and corrosion rate increased for the as-fabricated porous high-N austenitic stainless steel. Among others, the alloy with 10% (mass fraction) pore former exhibits the best corrosion resistance. Besides, the increase of sintering temperature can enhance the densification of the as-prepared alloy, thus improves its corrosion resistance.