Microstructure And Mechanical Properties Of TLP Bonding Joints Of GH3128 Superalloy

In this study,TLP welding was utilized to bond GH3128 nickel-based superalloy with 30?m BNi-2 amorphous foil as filler metal.The objective of this study is to avoid defections of solid state diffusion welding and improve the quality of the joints,based on the unique features of TLP.During the research,the evolution of microstructure and mechanical properties of joints over time were recognized and analyzed.And a new TLP process,which consists different combination of holding time and pressure applied at isothermal solidification and solid state homogenization,named homogenization with low-temperature and high-presure(HLH)process was designed and carried out based on the data of high-pressure TLP experiments.It was proved that this new technology can fully exploit the potencial of GH3128 superalloy,and can be strongly helpful to gain better understanding of TLP bonding and extend the scope of its application.The microstructure evolution of ASZ?ISZ?DAZ in TLP joints during isothermal solidification and solid state homogenization over time under the parameter of 1100?/1MPa was observed in detail.The elements distribution of joints and morphology,distribution,composition of precipitates was surveyed with EDS and SEM.The connection between microstructure and mechanical properties was thoroughly studied based in view of width of no-precipitation area and precipitation residual area,hardness distributon,and tensile strength at room temperature.It was proved that high level of homogenization can strongly improve the performance of the joints.The morphology and path of fractures were observed and the cause of it is confirmed,which is useful to get better TLP joints.It is proved that DAZ was the weakest area of joints due to the splitting effect of the second-phase precipitates generated in the DAZ during the TLP welding process on the substrate.With the prolongation of holding time in homogenization,the extent of elements interdiffusion increased,the quantity of precipitates in DAZ decreased,and the room-temperature mechanical properties of the joints increased.When the holding time reached 240min,the joint's room temperature tensile strength reached the highest valueThe experiment under the condition of 1100?/120min/10MPa was implemented and its beneficial effects on properties of TLP joints were confirmed.Howere,the dimentional accuracy of joints under high-pressure was deteriotaed.In order to solve this problem,and retain the benefits of pressure at the same time,HLH TLP welding process was designed and carried out.This new method,which applied high-level pressure and redued the temperature during solid state homogenization,has a promising prospect of application.The tensile strength of 1050? HLH joint reached 91.9%of base metal.