摘要
目的探究变激光能量/冲击次数无涂层激光冲击强化对12Cr2Ni4A钢力学性能和表面完整性的影响。方法采用Nd:YAG激光器对12Cr2Ni4A钢表面进行无涂层激光冲击强化处理,通过表征分析测试,对比分析未强化试样、无涂层激光冲击强化试样的显微硬度、显微组织、残余应力、表面粗糙度和表面形貌的变化规律。结果经强化处理后,近表层发生了塑性变形,形成了高密度位错,并诱发残余奥氏体向马氏体转变。显微硬度随着能量的增加呈先升后降的趋势,在70、100、130 mJ单次冲击下分别达到574.78HV0.5、605.52HV0.5、591.85HV0.5,相较于基体显微硬度(552.18HV0.5),分别约提升了4.1%、9.7%、7.2%。在130 m J条件下,当冲击次数增至2、3时,硬度的增幅分别为6.7%、3.7%,呈非单调变化。残余压应力峰值位于次表面约50μm处,随着能量的增加,由520.71 MPa升至666.2 MPa。在同一能量下,通过多次冲击可将残余压应力峰值进一步提高至776.2 MPa。此外,强化后试样的表面粗糙度和表面形貌演变受到激光冲击强化的机械-热效应协同调控,演变规律随着激光能量和冲击次数的变化并非呈单调变化。综合来看,130 mJ单次冲击可实现硬度梯度与残余应力的最优匹配。结论激光能量和冲击次数对12Cr2Ni4A钢力学性能和表面完整性的影响呈非线性,增加激光能量和冲击次数能够提升试样的残余压应力,但是对显微硬度的提升呈非单调递增,这归因于高能量和多冲击次数带来的位错饱和、热损伤效应。为了实现航空齿轮、花键等关键部件的高性能激光冲击强化加工,应综合考虑激光能量和冲击次数的影响,探究最优的强化工艺。
This study investigates the effects of laser shock peening without coating(LSPwc)on the mechanical properties and surface integrity of 12Cr2Ni4A steel,with a focus on optimizing laser energy and impact counts to enhance its performance for aerospace applications.Experiments are conducted using an Nd:YAG laser system(wavelength:532 nm,pulse width:8 ns,spot diameter:0.6 mm)under a coaxial water-jet configuration.The process parameters include laser energies of 70,100,and 130 mJ,an overlap rate of 50%,a repetition frequency of 50 Hz,and impact counts of 1,2,and 3 at 130 mJ.The microhardness,microstructure,residual stress,surface roughness,and surface morphology of both untreated and LSPwc-treated samples were systematically characterized and compared.The results indicate that LSPwc induces plastic deformation in the near-surface region of 12Cr2Ni4A steel,forming a high-density dislocation structure and promoting the transformation of residual austenite to martensite,thereby enhancing microhardness and residual compressive stress.In terms of microhardness,with the increase of laser energy,the hardness of the treated samples reaches 574.78HV0.5,605.52HV0.5,and 591.85HV0.5,representing increases of 4.1%,9.7%,and 7.2%,respectively,compared with the untreated sample.Under the same laser energy(130 mJ),as the impact counts increase,the microhardness improvements are 6.7%and 3.7%.Residual stress analysis demonstrates that the maximum compressive residual stress occurs at a subsurface depth of about 50μm,with values of 520.71,611.66,and 666.2 MPa for energies of 70,100,and 130 mJ,respectively.The affected layer depth increases with energy,reaching 400μm at 130 mJ.Multiple impacts at 130 mJ further enhance the peak residual stress to 722.8 MPa(2 impacts)and 776.2 MPa(3 impacts),with corresponding depths extending to 500 and 550μm.Kernel Average Misorientation(KAM)maps confirm intensified plastic deformation and increased dislocation density in the treated samples,consistent with the residual stress profiles.Surface roughness(Surface Arithmetic Average Height,Sa:The arithmetic mean of the absolute values of the height differences between all points in the sampling area and the reference plane.)exhibits a non-monotonic trend with increasing laser energy:it increases at 70 mJ due to localized plastic deformation and micro-cracking,decreases at 100 mJ as uniform plastic flow smoothed surface asperities,and rises again at 130 mJ owing to dominant thermal effects such as micro-melting and resolidification.Similarly,increasing the number of impacts leads to progressive roughness deterioration,attributing to cumulative plastic deformation and thermal damage.AFM topography further illustrates the evolution of surface morphology,with maximum peak-to-valley heights increasing significantly under high-energy and multi-impact conditions.Overall,a single impact at 130 mJ achieves the optimal balance between the hardness gradient and residual stress distribution.Furthermore,the evolution of surface roughness and morphology in the treated samples is governed by the combined mechanical-thermal effects of laser shock peening.The trends of these changes with variations in laser energy and impact count are non-monotonic.This investigation reveals that the influence of laser energy and impact counts on the mechanical properties and surface integrity of 12Cr2Ni4A steel is nonlinear.While increasing laser energy and impact count enhances the residual compressive stress,the improvement in microhardness does not follow a monotonic trend.This behavior is attributed to dislocation saturation and thermal damage effects induced by high energy levels and multiple impacts.To achieve high-performance laser shock peening for critical components such as aircraft gears and splines,it is essential to consider the combined effects of laser energy and impact counts and identify the optimal strengthening parameters.
作者
谢岑超
于水游
王珂
张少华
王荣平
陈超
XIE Cenchao;YU Shuiyou;WANG Ke;ZHANG Shaohua;WANG Rongping;CHEN Chao(National Key Lab of Aerospace Power System and Plasma Technology,Air Force Engineering University,Xi'an 710038,China;Army Aviation Military Representative Office in Tianjin,Tianjin 300000,China;Army Aviation Military Representative Office in Chengdu,Chengdu 610000,China)
出处
《表面技术》
北大核心
2025年第23期188-196,252,共10页
Surface Technology
基金
国家重点研发计划(2022YFB4601703)。
