新型多尺度碳氮化物强化马氏体耐热钢的稳定性

A Newly Developed Martensitic Heat-resistant Steel Strengthened by Multi-sized Carbonitrides

提出了一种新型多尺度碳氮化物强化马氏体耐热钢的组织模型。首先,通过降C和去除Mo、B的成分设计原则,分别抑制M_(23)C_6长大动力学,进而降低其粗化速率;抑制(Fe,Cr)_2Mo型Laves相的形成,进而降低M_2X型Laves相的粗化速率;减少硼化物脆性相的生成等,以优化组织结构。其次,通过改进形变诱导析出+热处理的方法,最终获得尺度主要分布在50nm以下和100～200nm这两个范围内的形状多样的碳氮化物析出相。本工作研制的新型碳氮化物强化马氏体耐热钢由于含有多尺度碳氮化物的不同强化机制,基体位错密度提高,亚晶界强化作用增强。经650℃高温时效1 000h,其马氏体板条未发生明显变化,基体表现出优良的高温稳定性。同时与传统工艺制得的耐热钢相比,其初始强度基本不变,但随着高温时效时间的延长,其硬度降低较小,性能退化缓慢。

The microstructural model of a new type of multi-sized carbonitrides strengthened Martensitic heat-resistant steel model was proposed in this paper.Firstly,decrease the carbon content and remove Mo and B so as to attenuate the growth kinetics and retard the coarsening of M 23 C 6 during aging,meanwhile minimize the coarsening rate of M 2X type of Laves phase and reduce the fragile borides in the matrix.Then,adjust the deformation temperature,the deformation rate,the stress relaxation time and optimize the heat treatment procedure to finally obtain the multi-sized carbonitrides which consist of various forms of M 23 C 6 and MX phases with the size ranging within 0-50 nm and 100-200 nm.By using the designed model,we successfully developed the novel carbonitride-strengthened heat-resistant steel,which showed excellent primary strength and high temperature microstructure stability.The small sized precipitates(below 50 nm)were designed to strongly strengthen the matrix by cumbering the movement of dislocations during creep,while the 100-200 nm particles mainly contribute to the formation of sub-grain boundaries and the stability of the lath boundaries and the prior austenite boundaries.With the help of these two types of carbonitrides,the sub-grain boundaries barely changed during aging at 650℃for 1 000 h.However,the hardness decreased slowly as the time extended,as compared with the steel produced by the traditional procedure.