真空渗碳18CrNiMo7-6钢中碳化物的析出规律

采用淬火膨胀仪进行模拟试验,通过对18CrNiMo7-6钢的显微组织、硬度分布的表征,研究了经真空渗碳后18CrNiMo7-6钢在冷却过程中碳化物的析出规律。结果表明,在980 ℃保温30 min后,试验钢中的碳化物完全溶解;快速冷却至600 ℃保温20 min后,渗层组织充分转变为细片层珠光体形貌组织;再升温至830 ℃保温20 min并以20 ℃/s的冷速气冷至室温后,室温组织出现不同形态的碳化物,马氏体组织较热处理前的原始组织得到了细化,且硬度及淬硬层深度较热处理前显著提升。

Carbide precipitation law in vacuum carburized 18CrNiMo7-6 steel

Using quenching dilatometer for simulation, carbide precipitation law during cooling of the vacuum carburized 18CrNiMo7-6 steel was studied by characterizing the microstructure and hardness distribution. The results show that after austenitizing at 980 ℃ for 30 min, the carbides are completely dissolved. After cooling quickly to 600 ℃ and holding for 20 min, the infiltration layer microstructure is fully transformed into fine lamellar microsturcture with pearlite morphology. Then after heating to 830 ℃ and holding for 20 min and cooling with protective atmosphere at 20 ℃/s to room temperature, carbides with different shapes appear, and the martensite is finer than that in the original microstructure before the heat treatment. Besides, the hardness is higher and the depth of hardened layer is deeper than those before the heat treatment.