氢对含(Ti,Mo)C析出相的调质马氏体钢的超高周疲劳性能的影响

The effect of hydrogen on the very high cycle fatigue properties of quenched and tempered martensitic steels containing (Ti,Mo)C precipitates

摘要:

本文研究了含有两种不同类型(Ti,Mo)C析出相的两种高强度马氏体钢充氢和不充氢时的超高周疲劳性能。结果表明：球形未溶(Ti,Mo)C析出相和非金属夹杂物的氢解吸附激活能分别为142.6和70.9 kJ/mol,这两种强氢陷阱在电化学充氢条件下不会捕获氢；位错和晶界处的可逆氢的解吸附激活能为16.9 kJ/mol,这部分氢扩散系数较大,室温放置96 h就能全部扩散出试样,在循环载荷下这部分氢能够迅速向裂纹尖端或应力集中处扩散,显著降低疲劳裂纹扩展应力强度因子门槛值,最终显著降低超高周疲劳强度；细小的回火(Ti,Mo)C析出相捕获的氢的解吸附激活能为17.0 kJ/mol,这部分氢的扩散系数较小,室温放置336 h仍不能扩散出试样,在循环载荷下这部分氢能够从氢陷阱处解吸附并且向裂纹尖端或应力集中处扩散,仍能一定程度降低钢的超高周疲劳强度,考虑到两者捕获的氢含量大致相当,被细小的回火(Ti,Mo)C析出相捕获的氢对超高周疲强度的有害作用要远小于位错、晶界处的可扩散氢对超高周疲劳强度的有害作用。

Abstract:

In the present study, the very high cycle fatigue properties of two high strength martensitic steels containing two different types of (Ti,Mo)C precipitates with and without electrochemical hydrogen charging were investigated. Results revealed that spherical undissolved (Ti,Mo) particles and non-metallic inclusion with a hydrogen desorption activation energy of 142.6 and 70.9 kJ/mol, respectively could not trap hydrogen through electrochemical charging; diffusible hydrogen trapped by dislocations and grain boundaries with a desorption activation energy of 16.9 kJ/mol could rapidly diffuse to crack tip or stress concentration field then reduced the threshold value of stress intensity factor (SIF) of crack growth remarkably, resulting in a decrease of fatigue strength, this portion of hydrogen could diffuse out of sample after atmosphere exposure for 96 h and would have no deleterious effect on fatigue strength; hydrogen trapped by fine, temper-induced (Ti,Mo) precipitates with a desorption activation energy of 17.0 kJ/mol could not diffuse out of sample even atmosphere exposure for 336 h, however could desorb from the trap site under cyclic loading then diffuses to the crack tip or stress concentration field, resulting in a decrease in fatigue strength. Considering the hydrogen content in each hydrogen trapping site the deleterious effect of hydrogen trapped by fine, temper-induced (Ti,Mo) precipitates was relatively small compared to the diffusible hydrogen trapped by dislocations and grain boundaries.