复合表面改性对M50NiL钢拉压疲劳寿命的影响

Effect of composite surface modification on tension-compression fatigue life of carburized M50NiL steel

为提高M50NiL钢的疲劳性能,在对M50NiL钢进行渗碳处理的基础上,分别进行单一磨料水射流喷丸、磨料水射流喷丸+表面超声滚压复合表面改性处理试验,研究表面形貌、表面粗糙度、残余应力场、表层硬度和疲劳寿命的关系。研究结果表明:与单一磨料水射流喷丸处理相比,复合表面改性处理可提高试样表面完整性。在表面形貌方面,复合表面改性处理试样获得了更完整的表面形貌,表面粗糙度降低了80%以上;在残余应力方面,复合表面改性处理试样最大残余压应力和最大残余应力场深度均大幅提升,表面残余压应力绝对值从870 MPa提升至1398 MPa,残余应力场深度从400μm提升到600μm;在硬度方面,复合表面改性处理试样获得了较高的硬度。在单一磨料水射流喷丸处理的基础上,复合表面改性处理进一步提升了渗碳M50NiL钢的疲劳寿命,在最大应力水平σ_(max)=800 MPa,应力比R=−1条件下,其拉压疲劳寿命较渗碳处理试样的疲劳寿命提高48.6倍,较单一磨料水射流喷丸处理试样的疲劳寿命提高1.1倍。复合表面改性处理试样疲劳寿命提升是残余压应力场、表面硬化及表面形貌改善的综合作用。

In order to improve the fatigue performance of M50NiL steel,on the basis of the carburizing treatment of M50NiL steel,single abrasive water jet peening,abrasive water jet peening+ultrasonic surface rolling process composite surface modification process tests were carried out,respectively.The relationship between surface morphology,surface roughness,residual stress field,surface hardness and tension-compression fatigue life were investigated.The results show that compared with single abrasive water jet peening,the composite surface modification process improves the surface integrity of the sample.In terms of surface morphology,the composite surface modification process has obtained a more complete surface morphology,and the surface roughness has been reduced by more than 80%.In terms of residual stress,after the composite surface modification treatment,both the maximum residual compressive stress of the sample and the maximum depth of the residual stress field greatly increase,the absolute value of the surface residual compressive stress increases from 870 MPa to 1398 MPa,and the residual stress field depth increases from 400μm to 600μm.In terms of hardness,the composite surface modification process achieve the highest hardness.On the basis of single abrasive water jet shot peening,the composite surface modification treatment can further improve the fatigue life of carburized M50NiL steel.When the maximum stress levelσ_(max) is 800 MPa and R is−1,the tension-compression fatigue life is 48.6 times longer than that of the carburized sample and 1.1 times longer than that of the single abrasive water jet peening sample.The increase in fatigue life of sample after the composite surface modification process is caused by the combined effect of the residual compressive stress field,surface hardening and surface topography improvement.