激光工艺参数对激光选区熔化牙科钴铬合金孔隙、表面粗糙度和硬度的影响

Effect of laser process parameters on the pores,surface roughness,and hardness of laser selective melting of dental cobalt-chrome alloys

目的为应对义齿加工厂在制备基于激光选区熔化(SLM)技术的牙科钴铬合金口腔修复体时因高孔隙率引发的质量问题,探究了不同成型工艺参数对材料微观结构及性能的影响机制,并据此精确界定了能够有效降低缺陷的口腔修复体成型工艺参数范围。方法通过调整SLM过程中的打印参数,探讨激光功率、扫描速度以及扫描间距对牙科钴铬合金成型件孔隙特性、表面粗糙度及硬度的影响。借助金相微观分析结合图像分析和熔池模拟技术,揭示孔隙的形成机制,并阐明了SLM牙科钴铬合金孔隙率与能量密度之间的关联。结果线能量密度高于0.18 J/mm时,熔池底部易出现气孔缺陷;激光能量密度低于0.13 J/mm时,熔池间隙内则因粉末未充分熔化而产生缺陷。尤其是当线能量密度超出0.30 J/mm或低于0.12 J/mm的阈值时,孔隙率显著升高至超过1%。此外,SLM牙科钴铬合金的自由面粗糙度与能量密度之间呈负相关关系,宏观硬度与孔隙率之间呈反比关系。结论基于本研究采用的原材料及成型设备条件,成功确定了SLM成型件孔隙率低于1%的关键工艺参数。具体而言,这些关键参数涵盖了线能量密度,其取值范围为0.13~0.30J/mm,同时,扫描间距应严格控制在90μm以下。

Objective To address the quality problems caused by high porosity in the preparation of dental cobaltchrome alloy prosthetics based on selective laser melting(SLM)technology,we investigated the influence mechanism of different forming process parameters on the microstructure and properties of the materials.Moreover,the range of forming process parameters that can effectively reduce defects was precisely defined.Methods The effects of laser power,scanning speed,and scanning distance on the pore properties,surface roughness,and hardness of dental cobalt-chrome alloy were investigated by adjusting the printing parameters in the process of SLM.Through metallographic analysis,image analysis,and molten pool simulation,the pore formation mechanism was revealed,and the relationship between the porosity and energy density of SLM dental cobalt-chrome alloy was elucidated.Results When the linear energy density was higher than 0.18 J/mm,the porosity defect easily appeared at the bottom of the molten pool.When the laser energy density was lower than 0.13 J/mm,defects occurred in the gap of the molten pool due to insufficient melting of powder.In particular,when the linear energy density exceeded the threshold of 0.30 J/mm or was below 0.12 J/mm,the porosity increased significantly to more than 1%.In addition,we observed a negative correlation between free surface roughness and energy density and an inverse relationship between macroscopic hardness and porosity.Conclusion On the basis of the conditions of raw materials and molding equipment used in this study,the key process parameters of SLM of molding parts with porosity lower than 1%were successfully determined.Specifically,these key parameters included the line energy density,which ranged from 0.13 J/mm to 0.30 J/mm,and the scan spacing should be strictly controlled below 90μm.