碳含量对注射成形HK30不锈钢显微组织与力学性能的影响

Effect of carbon content on microstructure and mechanical properties of metal injection molded HK30 stainless steel

针对实际生产中注射成形HK30不锈钢碳含量较高导致其性能下降的问题,本研究在喂料中添加石墨来改变注射成形HK30奥氏体不锈钢的碳含量,研究碳含量(质量分数,下同)对HK30不锈钢显微组织与力学性能的影响。结果表明,随碳含量从0.02%增加至0.49%,HK30奥氏体不锈钢的氧含量降低,材料的孔隙减少,相对密度、硬度和抗拉强度都提高;随碳含量增加,不锈钢晶界处逐渐析出M23C6型碳化物,少量晶界碳化物的析出能强化晶界,使材料硬度与强度都显著提高,但碳含量从0.18%增加至0.49%,烧结阶段液相量大幅度增加,材料出现过烧,并且晶界碳化物异常长大,达到3~5μm,材料的伸长率显著减小到26%。当碳含量控制在0.18%时材料性能最优,硬度(HV)达到162.81,相对密度为96.4%,抗拉强度和伸长率分别为589.96 MPa和45.7%。

To solve the problem of performance degradation due to high carbon content in injection molding HK30 stainless steel, the graphite was added to adjust the content of carbon. The effects of carbon content on microstructure and mechanical properties of metal injection molded HK30 stainless steel were investigated. The results show that the content of oxygen and the number of pores in samples decrease, and the relative density, hardness and tensile strength increase with increasing carbon content from 0.02% to 0.49%. The phase of M23C6 precipitats gradually at the grain boundary with the increase of carbon content. The carbides can improve the mechanical properties by strengthen the grain boundaries. When increasing carbon content from 0.18% to 0.5%, the content of liquid phase increases sharply in the sintering procedure, resulting in oversintering and the carbides grain at the boundary grows up abnormally to 3？5 μm, the elongation decreases to 26%. The optimal properties with the hardness of 162.81 HV, the relative density of 96.4%, the tensile strength of 589.96 MPa and the elongation of 45.7% are obtained when the carbon content is 0.18%.