原位微米/纳米TiC颗粒弥散强化304不锈钢的高温蠕变特性

High Temperature Creep Characteristics of In-Situ Micro-/Nano-meter TiC Dispersion Strengthened 304 Stainless Steel

以304SS不锈钢为母合金采用原位合成工艺制备微米/纳米TiC颗粒弥散强化304不锈钢(TiC-304SS强化钢),研究了强化钢和母合金的高温蠕变性能。结果表明:原位生成的TiC颗粒大多呈多边形,在母合金中均匀分布且与其良好结合。TiC颗粒的加入对强化钢的母合金晶粒有明显的细化作用。在700/100 MPa蠕变条件下母合金304SS蠕变后晶粒明显长大,且沿应力方向拉长。而TiC颗粒的加入抑制了母合金晶粒的长大,阻止了蠕变变形。显微组织和蠕变性能的结果表明,在强化钢和母合金的蠕变过程中位错的运动符合位错攀移机制。但是与304SS母合金相比,TiC颗粒的加入提高了TiC-304SS强化钢的蠕变表观应力指数和蠕变激活能。门槛应力、载荷传递和微结构的增强,是Ti C-304SS强化钢的蠕变增强特征。

Micro-/nano-metered Ti C particulates dispersion strengthened 304 stainless steel(TiC-304 SS strengthened steel)were prepared by in-situ reaction technology with 2%and 5%TiC(in volume fraction)respectively.The high temperature creep properties of the plain 304 SS and two TiC-304 SS strengthened steels were investigated.The results show that the in situ formed TiC particulates,most of which exhibited polygonal shape,were distributed uniformly in the matrix of 304 SS and are well bonded with the matrix.Moreover,TiC particulates present a significant effect on the grain refinement of the steel matrix.It reveals that being subjected to creep test by100 MPa at 700 oC for 200 h,the grains of the plain304 SS grew up evidently with elongated shape along the loading direction,in the contrary,the grain growth tendency of the TiC-304 SS strengthened steels seems to be inhibited,thereby,the creep deformation was effectively reduced.The above results imply that dislocation motion in the three steels accords with dislocation climb mechanism.Besides,the values of apparent creep stress exponent and activate energy of the two Ti C-304 strengthened steels are higher than that of the plain 304 SS.It is proposed that the enhancement of creep performance of TiC-304 SS strengthened steel may be ascribed to the enhanced threshold stress and load transfer barrier,as well as the microstructural strengthening effect.