Study On Process And Performance Of Mo-Si-B Alloy Manufactured By Selective Laser Melting

As the performance requirements for superalloys are getting higher and higher,Fe-Nibased superalloys can no longer meet the design requirements,and there is an urgent need for superalloys that can be used at higher temperatures.Molybdenum-based alloys are one of the main breakthrough research directions.The superalloy itself has an ultra-high melting point and requires higher melting equipment.Therefore,powder metallurgy technology has become the main method for processing and manufacturing superalloys.This experiment is based on Mo-Si-B series alloys in molybdenum-based alloys,using selective laser melting technology as a processing method,trying to explore the appropriate process parameters and methods for forming Mo-Si-B series alloys by selective laser melting technology.The influence of alloying elements in this forming method has been studied.Use Fluent software to perform thermodynamic simulation of the molten pool,analyze and judge the shape and size of the molten pool,select the appropriate combination of parameters according to the comparison between the molten pool size and the given powder layer parameters,and use Ansys Additive software to determine the overall forming result the calculation is performed,and the heat source parameter combination of 300 W and 500mm/s is selected according to the calculation results.This result was verified by actual printing,which confirmed the reliability of this parameter combination.The actual printing of the Mo-4.5Si-2B alloy formed by SLM using the selected parameter combination confirmed the validity of the simulation results,and the microscopic observation of the printed structure and defects was carried out to study the actual influence of the forming method.It is observed that there are only pure Mo and Mo solid solution phases in the Mo-4.5Si-2B molded parts,but the size gap between the grains is large,and there is a clear regional difference between the large grains and the small grains,and the stress distribution And the grain boundary distribution verifies that the generation of small grains is mainly caused by large internal stress,and cracks are generated when the grains cannot be further refined to release the stress.Therefore,the cracks mostly appear in the concentration and orientation of small grains.Areas with large differences.Three different alloy compositions are selected,Mo-4.5Si-2B,Mo-4.5Si-3.5B,and Mo-5Si-5B as the research objects,and the influence of alloying elements on the laser melting forming method of the selected area is further explored.The forming results show that there is no The increase in the content of shaped alloying elements Si and B will cause a significant decrease in density.And when the content of alloying elements is high,the T2 phase and T1 phase and the inclusion of alloying elements appear,which indicates that there are obvious deficiencies in the mixed powder for SLM processing and forming,and the smelting is insufficient.The mechanical properties are consistent with the densification results,and are less affected by the phase composition.When the densities is 93.5%,the bending strength is 46.53 GPa and the fracture toughness is 2.94 MPa√m The Mo-Si-B alloy formed by selective laser melting has a certain degree of plasticity,but mainly shows obvious brittleness,and the heat treatment process will significantly reduce the performance.During the initial oxidation process at 1000℃,it showed a certain degree of improvement in oxidation resistance,forming a flat surface different from the molybdenum trioxide flakelike structure,but limited by the holes and cracks in the processing process,the oxidation process started at the beginning The stage will proceed through defects,so that the protective effect of the surface oxide film is not effective,and there are also holes on the surface that hinder the formation of a dense oxide film.