Microstructure And Properties Of MP159 Superalloy Rolled By Liquid Nitroge

MP159 superalloy is a must-selected material for bearing bolts of aero-turbine engines.At the same time,improving the strength and plasticity of the alloy is a key engineering problem to be solved urgently in the aviation field.In order to overcome the problem of"strength-plasticity constraint"of MP159 superalloy.In this present work,liquid nitrogen rolling processing was proposed for MP159 superalloy by using cryorolling,which introduces a large number of dislocations,stacking faults and deformation nano-twins through cryorolling,thus solving the strength-plasticity matching problem of MP159 superalloy.In addition,by using SEM,EBSD and HRTEM methods,exploring the formation mechanism of deformation nano-twins in MP159 superalloy during cryorolling,and studied the effect of grain size,dislocation density and deformation nano-twins spacing on the room temperature,high temperature mechanical properties and hot corrosion resistance of MP159 superalloy.The main contents are as follows:（1）The microstructure evolution mechanism of MP159 superalloy during RTR and CR processing was studied by using XRD,EBSD and HRTEM methods.Under the same rolling reduction,the grains size was finer and the density of dislocations was higher in the CR specimens than that in the RTR specimens.Moreover,the deformation nano-twins and L-C locks can be formed for the RTR and CR specimens.The strengthening mechanism of the MP159 superalloy during RTR and CR processing is mainly ascribed to the dislocation strengthening,grain refinement strengthening and deformation nano-twins strengthening.Through the strengthening superposition model,the contributions of dislocation strengthening,grain refinement strengthening and deformation nano-twins strengthening to the mechanical properties of the alloy were quantitatively analyzed.（2）The high temperature mechanical properties of the RTR48 and CR48specimens were investigated by using EBSD and TEM methods.The UTS of CR48specimens decreased with the increase of tensile temperature and the decrease of tensile rate,while the fracture strain first decreased and then increased with the increase of tensile temperature.For the RTR48 specimens,the UTS first decreased and then increased with increasing tensile temperature,while the fracture strain increased.Deformation nano-twins can still remain stable at high temperature and improve the high temperature mechanical properties of the alloy.（3）The hot corrosion behavior and mechanism of MP159 superalloy were analyzed by using SEM、EDS、TEM and first-principles calculations methods.During hot corrosion test,only some short rod-likeγ′phases were generated for the RTR48specimens,while a lot of long rod-likeγ′phases were also generated apart from short rod-likeγ′phase for the CR48 specimens.The long rod-likeγ′phase with a large number of stacking faults and deformation nano-twins is considered to be an effective diffusion channel of alloy elements,which is conducive to the outward diffusion of Cr element to form a Cr₂O₃ oxide film,thereby significantly improving the hot corrosion resistance of the CR48 specimens.