Study On Selective Laser Melting And Heat Treatment Process Of Cobalt-chromium Alloy Denture

The selected laser melting technology(SLM)has the characteristics of being able to form a complex structure,good performance and high-precision parts.It can meet the requirements of medical personalization and high precision,and has a broad application market in the medical field.Cobalt-chromium alloys are widely used in joint implants and dental fields due to their excellent mechanical properties,corrosion resistance and wear resistance.At present,there is no standard for the application of SLM-formed cobalt-chromium alloy in the dental field at home and abroad.This study uses cobalt-chromium alloy powder as raw material,from the aspects of microstructure,mechanical properties and corrosion resistance to SLM forming and heat treatment.Cobalt-chromium alloys have been evaluated and are of great importance for the development of standard specifications for the preparation of cobalt-chromium alloy dentures by SLM.The main research contents are as follows:(1)In the process of SLM forming cobalt-chromium alloy,firstly,the orthogonal test method is used to study the influence of laser power,scanning speed and scanning line spacing on the density of molded parts.By analyzing the orthogonal test results,three results are obtained.The influence law of the factors on the density of the part is used.Then the response function surface method is used to establish the quadratic function model between the density and the three influencing factors to re-optimize the molding process,and the process parameters with a formable density of 99.8% are obtained: P =198W;S=0.04mm;V=874mm/s,and the microstructure analysis and phase detection of the formed parts were carried out.It provides better process parameters for the preparation of dentures with good performance in SLM.(2)In terms of dimensional accuracy and performance of molded parts,the dimensional accuracy of SLM molded parts was tested.It was found that the accuracy errors were generated in the three directions of X,Y and Z,and the causes of the errors were analyzed to solve the SLM molding.The accuracy of the denture has laid the foundation;the performance of the cobalt-chromium alloy has been tested and compared with the ASTM F75 standard.The results show that the performance of the SLM-formed cobalt-chromium alloy is better than that of the cast cobalt-chromium alloy.Using a metallographic microscope and scanning electron microscopy,it was found that the microstructure of the SLM molded parts was uniform and the crystal grains were fine.(3)In the heat treatment of molded parts,through the analysis of the performance of SLM molded parts,it is found that SLM molded parts have problems such as stress concentration and poor elongation at break.The heat treatment process of the molded parts is studied,and the heat treated parts are tested.The results show that the mechanical properties of the cobalt-chromium alloy after heat treatment are slightly decreased,and the elongation at break is improved.Through the heat treatment,the microstructure of the SLM molded parts is redistributed,and the performance defect of the parts is solved.Through the related research on SLM forming cobalt-chromium alloy,it provides a theoretical basis for its application in the field of dental denture implants.