增材制造钛合金激光喷丸强化表面完整性影响实验研究

Effect of Laser Peening on Surface Integrity of Additive Manufactured Titanium Alloy

增材制造具有产品开发快速性,能够直接生产出具有复杂几何形状的金属零件,同时显著提高材料的利用率、降低成本。增材制造零件在疲劳等关键性能上与锻件仍然存在一定的差距,需要探寻有效的后处理方法。采用激光喷丸强化增材制造TC4钛合金,研究增材制造TC4钛合金表面完整性改善效果,并与同牌号常规锻造钛合金进行强化效果对比。结果表明,激光喷丸对于两种材料表面粗糙度影响微弱。在硬度方面,增材制造TC4的表面显微硬度从348 HV增加到367 HV,影响层深度达0.75 mm,而常规锻造TC4表面显微硬度从315 HV提高到362 HV,影响层深度大于1 mm;在残余应力方面,激光喷丸在增材制造TC4表面所引入的残余压应力最大值约为400 MPa,受影响的区域深度约为0.75 mm,而常规锻造TC4表面所引入的残余压应力最大值约为600 MPa,受影响区域深度大于1 mm。此外,利用阿基米德法测量出增材制造TC4的致密度为98.46%,经过一次激光喷丸处理后提高到98.92%。与锻造TC4相比,增材制造TC4组织相对疏松,可能是导致激光喷丸所引入残余应力幅值较小,影响层深度较浅的原因。

Additive manufacturing can rapidly and directly produce metal parts with complex geometries,while significantly improving material utilization and reducing costs.Additive manufacturing parts still have a certain gap with forgings in key properties such as fatigue,and it is necessary to find an effective post-processing method.Additive manufactured TC4 was treated by laser peening,and the surface integrity improvement effect of TC4 titanium alloy was investigated.The strengthening effect was compared with the same grade conventional forged titanium alloy.The results show that laser peening has little effect on the surface roughness of the two materials.Furthermore,the surface microhardness of additive manufactured TC4 increased from 348 HV to 367 HV,and the hardening layer reached a thickness of 0.75 mm,while the surface microhardness of wrought TC4 increased from 315 HV to 362 HV,and the hardening layer reached a thickness more than 1 mm.Compressive residual stress was induced into the subsurface of the samples with a maximum value around 400 MPa for the additive manufactured TC4.The affected zone depth was around 0.75 mm.For the wrought TC4,the compressive residual stress was induced into the subsurface of the samples with a maximum value around 600 MPa.The affected zone depth was more than 1 mm.In addition,the density of additive manufactured TC4 was measured by the Archimedes method.The density of additive manufactured TC4 was 98.46%,while the density became 98.92% after one shock of laser peening.Compared with wrought TC4,the relative porosity of additive manufactured TC4 may be the reason for the smaller residual stress amplitude and shallow affected depth by laser peening.