Investigation On The Process And Propertie Of Mo-TiC-Si-B Alloys By Selective Laser Melting

The increasing demand for high-efficiency engines in the aviation industry requires breakthroughs in high-temperature technology.The application of ultra-high temperature materials can operate at higher temperatures than nickel-based superalloys,which improves engine efficiency by minimizing the inefficient loss of the cooling system.Traditional nickel-based superalloys are mainly used for aircraft turbine blades.Increasing the inlet temperature of the turbine can achieve higher energy efficiency.Since the melting point of the nickel-based superalloy is lower than the turbine inlet temperature during takeoff,a cooling system is essential.However,the cooling system limits the ability to improve operating efficiency,so people are increasingly looking forward to the development of new ultra-high temperature materials.Mo-based alloys are excellent candidates for ultra-high temperature applications.However,Mo-based alloys have oxidation resistance and room temperature brittleness Has always been an important issue.In this study,Mo-Ti C-Si-B alloy was used as the research material,and Mo-Ti C-Si-B alloy was formed by selective laser melting molding process.The composition design of the material in this study is based on the ternary phase diagram of the Mo-Si-B alloy,a reasonable alloy composition is selected,and Ti C is added to improve the oxidation resistance and room temperature brittleness of the alloy.The raw materials used for selective laser melting molding are spherical powders for selective laser melting molding.The optimal molding parameters,powder mixing,substrate selection,compactness of the sample after molding,phase analysis and structure characteristics,and samples are explored.The oxidation resistance and mechanical properties.Determine the reasonable range of process parameters through single-melt experiments,design orthogonal experiments to explore the most suitable experimental process parameters,perform three-dimensional modeling through UG,perform mesh division,material property definition,and mathematics in Simufact Additive Model establishment and process parameter definition.Finally,through the range analysis of the simulation results,the final process parameters are determined:250 W laser power,900 mm/s scanning speed,0.09 mm scanning distance,and 0.03 mm coating thickness.The actual selected area laser melting molding of the alloy was carried out through the determined process parameters,which verified the validity of the simulation results,and analyzed the density and structure of the molded samples.It was found that the overall density of the alloy was good,all above 97%.The structure has not only the eutectic structure similar to the traditional casting method,but also the dendritic structure peculiar to the selective laser melting molding.From the XRD pattern,it can be concluded that the main structure of the alloy is Mo_ss,Ti C and T₂ phases,and the results are consistent with the alloy phase diagram.Through the EBSD characterization,it is found that the IPF characterization of the horizontal and vertical directions of the sample is basically the same,but the crystal grains of the sample in the vertical direction are obviously finer than the horizontal direction;the horizontal and vertical directions of the sample promote the same degree of crystal grain rotation,And finally affect the orientation change,and then form the same texture type,the texture of the two is mainly concentrated between 60°-70°.Analyze the mechanical properties and oxidation resistance of the alloy formed by laser melting in the selected area.In all cases,the load increases almost linearly in the elastic region,and decreases as the displacement increases after reaching the peak.The zigzag flow behavior that may be caused by microcracks is often observed in the curves of all alloys,and the fracture mode is quasi-cleavage fracture.T₂ and B₂O₃·Si O₂ will hardly be corroded and consumed by high temperature oxygen environment.The alloy formed by the selective laser melting technology of adding Ti C realizes the refinement of the alloy phase and grain,and the T₂ and B₂O₃·Si O₂ phases are more uniformly distributed in the alloy.