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对高Nb含量的316LN奥氏体不锈钢,在650、750和800℃时效处理不同时间。通过定量金相,SEM、XRD及TEM等分析技术,分析了析出相随时效时间和温度的变化关系。结果表明:时效初期,析出相沿晶界呈颗粒状、短棒状析出,随时效时间延长析出相沿晶界呈链状析出,析出量不断增多,并逐渐向晶内生长,最终以不连续的片状布满整个晶面。750℃为时效敏感温度,该时效温度下,析出相的量最多,孕育时间最短。整个时效阶段,时效优先析出相为Z-Cr Nb N相,且作为氮化物的主要存在形式,而不是常见的ε-Cr2N相。316LN不锈钢中,Nb元素的添加,一定程度上抑制了ε-Cr2N相和Z-Cr23C6相的析出,加速了σ-FeCrMo相的析出。
316LN austenitic stainless steels with high Nb content were aged at 650, 750 and 800 ° C for different times. Through quantitative metallography, SEM, XRD and TEM analysis, the relationship between the precipitation time and the aging time was analyzed. The results show that in the initial stage of aging, the precipitates are precipitated along the grain boundary and precipitated in a short rod shape. With the aging time prolonged, the precipitates are precipitated along the grain boundaries. The amount of precipitates increases continuously and gradually grows into the grains. Finally, Full of crystal face. 750 ℃ is the aging sensitive temperature, the aging temperature, the largest amount of precipitation phase, incubation time is the shortest. Throughout the aging stage, the preferential precipitation phase is the Z-Cr Nb N phase, which is the predominant form of nitride rather than the common ε-Cr2N phase. The addition of Nb in 316LN stainless steel inhibited the precipitation of ε-Cr2N phase and Z-Cr23C6 phase to a certain extent and accelerated the precipitation of σ-FeCrMo phase.