The Study On Process, Microstructure And Properties Of CoCrMo Alloy Manufactured By Selective Laser Melting

CoCrMo alloy is one of the most common medical metal materials, which has excellent forming ability and good properties, and it has wide application prospect in the field of biomedicine. In recent years, the process of customized manufacture is speeding up with the development of additive manufacturing. Selective laser melting(SLM) is a representative technology in the field of metal additive manufacturing. The parts with complex structure, good property and high precision can be manufactured rapidly by SLM, which provide the basis for directly manufacturing of CoCrMo alloy in the field of medicine. In this study, the CoCrMo power satisfying the standard of ASTMF75 is used to manufacture some parts by SLM. The process and property is studied and analysed. The main contents include the following aspects:(1) In the process optimization, the key problems of processing are analyzed. Three important factors including laser power, scanning speed and scanning space are choosed to optimize and analyse the process. The interaction between factors is studied by the methods of orthogonal experiment and response surface.The relative density of the parts manufactured by the optimized parameters can reach 98%.The microstructure of CoCrMo alloy manufactured by SLM is observed and the component is tested. The results show that the parts mainly exist one phase at room temperature, the microstructure is dense and the morphology of the melting track is obvious. The changes the content of elements are very small after manufacturing, which also satisfies the requirement of ASTMF75.(2) In the forming quality,the surface accuracy, dimensional accuracy and defect detection of CoCrMo alloy manufactured by the optimized parameters are studied. Surface roughness of Co Cr Mo alloy manufactured by SLM is about 20 μm,and the roughness can be improved by different post-treatment process. Due to the processing mechanism, there are errors in the size and shape of the parts. But the offset ratio of all errors is under 1%. There are no defects in the parts, and the forming quality is better than parts manufactured by casting.(3) In the forming properties, the properties of CoCrMo alloy manufactured by SLM are studied, including mechanical properties, corrosion resistance and residual stress, etc. The results show that the intensity and corrosion resistence are better than parts manufactured by casting, but the toughness is lower and the distribution of stress is uneven. The CoCrMo alloy phase diagram is studied and the reasonable heat treatment experiment scheme is formulated. The properties of CoCrMo alloy manufactured by SLM are improved through the different heat treatment conditions, and eventually the comprehensive performance of the parts can satisfy the requirements of ASTMF75 standard.This research can provide basis for the application of CoCrMo alloy manufactured by SLM in the field of medical implants, which can bring a great significance for the customized manufacture of CoCrMo alloy.