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对P92钢进行650℃,0~8000h时效实验,采用SEM-BSE和定量金相技术对Laves相的体积分数、平均直径和数量密度进行定量,研究了Laves相的析出和粗化动力学特性,评估了Laves相演化对蠕变强度的影响.结果表明,Laves相在时效0~2000 h内析出,优先在晶界析出长大,最终析出时的体积分数约为0.95%.Laves相粒子在时效3000 h后明显聚集粗化,粗化速率明显快于M23C6碳化物的原因是由于晶界扩散机制的作用.Laves相在1000~3000 h内具有最佳的析出强化效果,超过3000 h后由于显著粗化使沉淀强化作用明显下降.由于体积分数小和热稳定性差,Laves相的强化作用远小于M23C6型碳化物.
The aging experiments of P92 steel at 650 ℃ and 0 ~ 8000h were carried out. The volume fraction, average diameter and number density of Laves phase were determined by SEM-BSE and quantitative metallographic techniques. The precipitation and coarsening kinetics of Laves phase were studied. The effect of Laves phase evolution on creep strength was evaluated.The results show that the Laves phase precipitates within 0-2000 h of aging, preferentially precipitates and grows at the grain boundary, and the final volume fraction of precipitation is about 0.95% After 3000 h, the coarsening and roughening rate was obviously faster than that of M23C6 carbides because of the grain boundary diffusion mechanism. The Laves phase had the best precipitation strengthening effect within 1000-3000 h, and after 3000 h, Coarsening reduced the precipitation strengthening obviously, and the strengthening effect of Laves phase was far less than that of M23C6 carbide due to its small volume fraction and poor thermal stability.