热辅助超声滚压温度场参数影响激光熔覆涂层表面粗糙度研究

Effect of Heating Parameters on Roughness of Laser Cladding Coatings Treated by Heat-assisted Ultrasonic Burnishing

目的降低激光熔覆涂层的表面粗糙度。方法采用激光熔覆技术制备铁基激光熔覆涂层,采用超声温滚压耦合热处理工艺对熔覆层进行熔覆后强化加工,重点研究温度场参数对成形表面粗糙度的影响,通过方差分析(ANOVA)确立参数显著性,同时利用响应曲面法(RSM)构建温度场参数影响铁基涂层表面粗糙度的预测模型,并进行参数优化。结果加热温度和保温时间对成形试样表面粗糙度的影响显著。在实验参数范围内,试样的表面粗糙度与加热温度呈正相关,与保温时间呈负相关。实验结果表明,在相同保温时间下,在加热温度100、250、400℃条件下试样的表面粗糙度Ra分别为0.237、0.158、0.096μm;在相同加热温度下,在保温时间为0.5、1、2 h条件下试样的表面粗糙度Ra分别为0.156、0.164、0.170μm。可见与保温时间相比,加热温度对涂层表面粗糙度的影响更显著。参数优化分析结果表明,在实验参数范围内,在400℃加热温度和0.5 h保温时间条件下,试样具有最小的表面粗糙度Ra(0.089μm)。结论相较于车削及常温滚压工艺,采用超声温滚压耦合热处理工艺可进一步降低激光熔覆涂层的表面粗糙度,在实验参数范围内,加热温度400℃和保温时间0.5 h是最优的温度场参数组合。

Laser cladding technique can save resource consumption,achieve rapid manufacturing and damage repair of high-end parts/components,and thus promote environmental sustainability.However,in most cases,the surface finishing of cladding parts/components cannot meet the requirements of engineering applications,and thus post-cladding processes are required.Here,a sort of post-cladding treatment,that is,ultrasonic warm burnishing coupled with sequent heat treatment(UWB/HT),was proposed and employed to treat coatings after laser cladding.Especially,based on experimental data,a prediction model of surface roughness of the studied Fe-based cladding coating was built.ANOVA and RSM methods were employed to investigate the effect of heating parameters,i.e,heating temperature and heat holding time,on roughness of laser cladding coatings treated by UWB/HT.According to result,the surface roughness of the studied coating was positively related to heating temperature.For instance,at a same holding time,the roughness values of coatings treated at 100℃,250℃and 400℃were Ra 0.237μm,Ra 0.158μm and Ra 0.096μm,respectively.Therefore,it was proved that UWB/HT process could further decrease coating roughness in comparison to traditional ultrasonic burnishing without heating treatment.However,in contrast,a long holding time was supposed to result in slight increase of coating roughness.For instance,at a same heating temperature,the roughness values of coatings treated at 0.5 h,1 h and 2 h were Ra 0.156μm,Ra 0.164μm and Ra 0.170μm,respectively.The warm plasticity of metal materials resulting from high temperature was responsible for the roughness decrease of coating treated by UWB/HT.Meanwhile,longer holding time led to somewhat deformation recovery of burnished coating and therefore resulted in slight roughness increase.According to ANOVA result,heating temperature had a more significant effect on coating roughness than holding time.Within experimental scope,the optimum parameter combination was 400℃heating temperature and 0.5 h holding time,under which a least roughness value of Ra 0.089μm was achieved.