Study On The Technology And Properties Of Selective Laser Melting Forming Of Titanium Alloy Dental Crowns

The traditional manufacturing method of dental crowns has low efficiency,long cycle and poor patient wearing comfort.As an advanced additive manufacturing technology,Selective Laser Melting(SLM)technology has the characteristics of high flexibility,high laser energy,and the ability to directly form complex structural parts,which has unique advantages for forming dental crowns.But thin-walled parts are prone to deformation defects in selective laser melting forming.In this paper,the Ti-6Al-4V titanium alloy is used as the experimental material,the crown is the research object,and the laser power,scanning speed and scanning distance are the variables to explore the influence of different laser energy densities on the deformation and performance of the formed parts,and optimize the forming process;The influence of heat treatment process on the structure,deformation and properties of the formed parts was discussed;in addition,according to two methods of heat treatment and non-heat treatment,the three-dimensional model of the crown formed under the optimized process was fitted with the original digital crown.The main research contents and conclusions are as follows:The traditional manufacturing method of dental crowns has low efficiency,long cycle and poor patient wearing comfort.As an advanced additive manufacturing technology,Selective Laser Melting(SLM)technology has the characteristics of high flexibility,high laser energy,and the ability to directly form complex structural parts,which has unique advantages for forming dental crowns.But thin-walled parts are prone to deformation defects in selective laser melting forming.In this paper,the Ti-6Al-4V titanium alloy is used as the experimental material,the crown is the research object,and the laser power,scanning speed and scanning distance are used as variables to explore the influence of different laser energy densities on the deformation and performance of the formed parts,and the forming process is optimized.The influence of the heat treatment process on the deformation,structure and properties of the formed parts was discussed,and the three-dimensional model of the formed crown under the optimized process and the original digital crown was fitted.The main research contents and conclusions are as follows:(1)By exploring the effect of laser energy density on the deformation and surface quality of Ti-6Al-4V titanium alloy parts formed by selective laser melting,the results show that when the laser energy density E is in the range of 32.83 J/mm~3 to 85.71 J/mm~3,as the laser energy density increases from low to high,the deformation and roughness of the formed parts show a trend of first decreasing and then increasing.Taking the amount of deformation as the measurement index,the optimized laser energy density is 68.18J/mm~3,that is,the combination of process parameters is:the laser power is 180 W,the scanning speed is800 mm/s,and the scanning spacing is 0.11 mm.(2)By exploring the effect of laser energy density on the density,Vickers hardness and mechanical properties of Ti-6Al-4V titanium alloy parts formed by selective laser melting.The results show that in a certain range of laser energy density,the density,Vickers hardness and mechanical properties of the formed parts all show a trend of increasing first and then decreasing.When the energy density is low,the Ti-6Al-4V titanium alloy powder absorbs less heat,causing unstable melt flow,resulting in large roughness of the formed parts,many defects,low actual density and low hardness;when the energy density is too high When sufficient,the metal powder absorbs a lot of heat,which is easy to lead to the occurrence of over-burning,which affects the quality of powder coating,increases the defects in the formed parts,and reduces the density and Vickers hardness of the formed parts.(3)By comparing the changes of deformation,structure and properties of parts before and after heat treatment,the results show that after heat treatment of formed parts,the degree of deformation is significantly reduced,the hardness and tensile strength are also reduced,and the elongation after fracture is improved.After annealing at 800?/4h,the microstructure of the part was transformed from acicular?'phase martensite to stable?+?phase,the residual stress and tensile strength of the part were reduced,but the plasticity was improved.(4)After optimizing the process parameters,the fitting results of the titanium alloy crown formed by selective laser melting technology and the original digital crown,hardness test results and roughness test results show that when the laser power is 180 W and the scanning speed is 800mm/s and the scanning interval is 0.11 mm,Ti-6Al-4V titanium alloy crowns with small deformation,high hardness and low roughness can be prepared,which can meet the needs of dentistry.In this paper,by optimizing the forming process,the optimal combination of process parameters for selective laser melting forming of titanium alloy crowns was obtained,and the effects of laser energy density and heat treatment process on the properties and microstructure of SLM formed Ti-6Al-4V titanium alloy parts were revealed.It provides some theoretical reference for selective laser melting forming of titanium alloy thin-walled parts.