Analysis On Performance Of Co-Cr Alloy With RF Plasma Spheroidization And SLM

Currently,cobalt-chromium alloy powder used for selective laser melting in the market are mainly used by foreign companies,due to the fact that imported powder have a high balling rate,powder flowability and other powder properties are better than domestic cobalt-chromium alloy powder.And most of the powder on the market for metal powder are produced by gas atomization.The main reason for this is that the method of gas atomization has high production efficiency.However,this method has certain drawbacks,such as the use of crucible oven to melt raw materials for gas atomization has many impurities.The use of raw materials as the electrode production method may have some electrode contamination,etc.Compared with the manufacturing methods of traditional spherical powder,RF plasma spheroidization utilizes a thermal plasma as the heat source.The heat source of RF plasma is pure and free from electrode contamination,and the RF plasma torch has a higher temperature,which can reach 10,000 K.It is also applicable to spheroidize metals which has high melting point.It also can be used for secondary reformation of powder materials,change its powder morphology,increase the sphericity of powder particles,reduce irregular powder and defective powder.Moreover,it can be use to treat the discarded metal powder to achieve the secondary use of waste powder.In this paper,it is performed that RF plasma spheroidization can extract cobalt-chromium alloys after many times of selective laser melting.Using a fixed-variable method to research on the spheroidizing process mainly included the powder feed rate,the pressure in the spheroidizing reactor,and the carrier gas flow rate.In order to obtain better process parameters,through the spherodized powder particles morphology and powder characteristics to characterize the spheroidizing effect is good or not.After many tests,better process parameters were obtained: the feed rate was 20 g/min,the internal pressure of the spheroidizer was 12 Psia,and the carrier gas flow rate was 6 slpm.Other process parameters center gas flow 40 slpm,sheath argon flow 75 slpm,voltage value 6.3 kv,power 15 kw,frequency 114.3Hz.The research in this paper provides a basis for the future production of RF plasma spheroidizing cobalt-chromium alloy powder.The research in this paper provides a basis for the future production of RF plasma spheroidizing cobalt-chromium alloy powder.The microstructure and properties of the cobalt-chromium alloy powder were compared and analyzed successively during the spheroidization.The spheroidized cobalt-chromium alloy powder was used for the comparative analysis of the microstructure and properties of the molded parts with SLM.The analysis results show that the degree of defect on the surface of the laser melting molded parts before and after the spheroidization is different,and thereare many holes before spheroidizing,but the microstructure is the same.All of them are submicron columnar crystals with sizes in the range of 0.3um-0.5 ?m.There is a certain heredity between the tissue of the molded part and the powdered tissue.The density,micro-hardness,and tensile properties of the small cubes printed with the spheroidized powder are all higher than those before the spheroidization,which shows that the overall performance of the spheroidized metal powder-printed molded part is improved,and the spherical shape is also indicated.The powder has a certain influence on the quality of the molded parts with SLM.