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一、引言沿晶断裂是高温蠕变断裂最普遍的形式。对沿晶断裂机制,Zener最先提出,当沿晶界发生滑动时,在三个晶粒交界处产生应力集中,引起裂纹的产生和扩展,造成沿晶断裂的应力集中论。后来Greenwood等提出,空位沿晶界聚集形成空洞,空洞逐渐长大,互相连接形成裂纹,导致沿晶断裂的空位聚集论。后一种理论是以扩散过程为基础的,称为扩散蠕变断裂。很多研究者对扩散蠕变断裂提出不同的物理模型试图计算蠕变应变和断裂时间,对特定的材料和试验条件,得到了和实验结果近似一致的结果。本文的目的是用扫描电镜研究火电厂用12CrlMoV钢制的高温高压蒸汽管,在蠕变过程中的损伤及断裂特征。试图为研究蠕变断裂时最小变形量及使用寿命终了退役的判断标准,寻找一种微观结构参量。
I. Introduction Intergranular fracture is the most common form of creep rupture at high temperature. For the intergranular fracture mechanism, Zener firstly proposed that the stress concentration occurs at the interface of three grains when sliding along the grain boundaries, resulting in the generation and propagation of cracks, resulting in the stress concentration theory of intergranular fracture. Later, Greenwood et al. Proposed that vacancies accumulate along the grain boundaries to form voids. The voids gradually grow up and connect with each other to form cracks, leading to vacancy aggregation along the grain boundaries. The latter theory is based on the diffusion process, called diffusion creep rupture. Many researchers propose different physical models of diffusion creep rupture in order to calculate creep strain and rupture time. For specific materials and test conditions, the results are approximately consistent with the experimental results. The purpose of this paper is to study the damage and fracture characteristics of high temperature and high pressure steam pipe made of 12CrlMoV steel in thermal power plant by means of scanning electron microscopy. Attempt to study the minimum deformation of creep rupture and end of life judgment criteria to find a microstructure parameter.