低碳贝氏体微观组织形态对冲蚀磨损性能的影响

Effects of Microstructure and Morphology on Slurry Erosion Performance of Low- Carbon Bainitic Steels

通过热处理改变低碳贝氏体钢中的奥氏体及其转变物(下称M/A)分布形态,调整钢响应载荷时的微观应力集中位置,并用弹塑性力学理论揭示了贝氏体钢较高的抗冲蚀磨损性能的力学机理.对比研究了相同化学成分贝氏体、珠光体和马氏体的冲蚀磨损性能,发现珠光体和马氏体因强度、韧塑性无法达到最佳匹配,其抗冲蚀磨损性能均不如贝氏体.在贝氏体钢中,粒状M/A贝氏体的应力集中位置使得冲蚀裂纹显著地向试样心部扩展,降低了抗冲蚀磨损能力.薄膜状M/A贝氏体的应力集中位置不利于表面裂纹向试样心部生长,实现了较高的抗冲蚀磨损性能.

An improved resistance of a low- carbon bainitic steel to slurry erosion was achieved by utilizing a heat treatment to alter the distribution map of M / A constituent,which refered to austenite and its transformation products. In light of elastic and plastic theorems such an improvement was attributed to that one particular M / A distribution had the capability to optimize the stress concentration intensity and therefore the erosion performance. The steel studied here was transformed into four different metallurgical structures: bainite with thin- film M / A,bainite with granular M / A,pearlite and martensite. It is found that pearlite and martensite had the worst erosion resistance due to the mismatch of strength and toughness,and that bainite with granular M / A also had a relatively low erosion resistance since the cracks on the erosion surface grew into the inner part of the steel resulting from the point of stress concentration itself extending inwards. Bainite with thin- film M / A,however,had the best erosion resistance because the particular stress concentration prevented cracks from propagating inwards.