高温回火对USS122G超高强度不锈钢显微组织的影响

 为了研究高温回火工艺对USS122G超高强度不锈钢显微组织和硬度的影响,采用扫描电镜、透射电镜、物理化学相分析等方法进行分析测试及表征。结果表明,随着回火温度升高,钢中的奥氏体体积分数及第二相数量呈减少趋势,680~700 ℃时第二相的平均尺寸约为65 nm,第二相强化效果减弱,此时硬度为36HRC~37HRC;700 ℃时第二相开始在晶界聚集,而温度高于720 ℃后,细小的第二相数量增加,第二相在晶界上形成了网状分布,硬度有增加趋势。钢的硬度变化主要受到第二相强化影响,综合高温回火对钢中奥氏体体积分数、第二相及硬度的影响,最终确定该钢的最佳高温回火温度为660~680 ℃。

Effect of high temperature tempering on microstructure of USS122G ultra-high strength stainless steel

In order to study the influence of various tempering process on the microstructure and hardness of USS122G ultra-high strength stainless steel. Using SEM,TEM,physicochemical phase analysis,testing and characterization. The results indicated that volume percent of the austenite and the number of second phase reduced with the increased of tempering temperature. When the temperature was 680-700 ℃,the average size of the second phase was about 65 nm. At this time,the strengthening effect of the second phase was smaller and the hardness of the sample was 36HRC-37HRC. At 700 ℃,the second phase aggregated at the grain boundary. When the temperature was higher than 720 ℃,the number of smaller second phase increased. The second phase was distributed in a network along the grain boundary and increased the hardness. The increased in hardness of steel was mainly affected by the strengthening of the second phase. Finally,the optimum tempering temperature of USS122G steel was 660-680 ℃,considering the influences of austenite volume percent,second phase and hardness.