Simulation And Experiment Verification Of Near Net Shape Hot Isostatic Pressing

Since the. powder material's non-dense properties and complex coupled environmental conditions during the hot isostatic pressing,making the part's final shape and size have a certain bias with the design,thus precise control of shape is the key and most difficult technologies in the near net shape processing. Numerical simulation method can predict the can's deformation and the powder's densification process during the hot isostatic pressing, which provide guidance for the can's shape optimization.In this paper,the Shima model is used in the simulation study of hot isostatic pressing by MSC.Marc Software. First, we simulate the 316 stainless steel powder's forming process of the cylindrical test sample, the results show that: the can's shape will have a significant contraction after the first expansion ,the can's axial contraction reached 7% and the radial contraction of the middle reaches 12%.The densification process show that, powder compact from outside to inside, from the middle to both ends. Based on the can's deformation study, we supposed the anti-distortion design method and finished the design of the turbine-disk's can and core structure. In the simulation of the Ni526 turbine-disk's hot isostatic pressing, the maximum compressive displacement of the cover can amounted to 7.82cm.The results show that the powder's density can reach to 96.9%, due to the non-ideal core and material parameters, the density distribution is not uniform, even low density existing.To verify the simulation results, we conducted the hot isostatic pressing technology. We produced the can components and the gas-pipes, Ni625 alloy powder's morphology parameter was tested and the method of the vacuum and cut processing was improved. 300℃~ 400℃heating was added in the vacuum processing, which can reduce the outgassing time. In the original cut processing, the pipe is easy cracking, this was improved by using the new cutting method. We got the cylindrical test samples and the turbine-disks to verify the simulation. Test points on the key positions are selected to verify the simulation accuracy. In the results of the cylindrical test samples, the radial displacement is larger about 1.86%,while 0.56% of the axial simulation results is smaller; counteraction in deformation caused the error ratio of density in simulation is only 4.23% to 6.45%.The turbine-disk's experimental results have a good agreement with the simulation, the shrinkage of key position is less than 10% and the deformation mainly concentrated in the inward compression of the can's sleeve top and the radial contraction of the packet sides. After selective pickling and machining,the density of the turbine-disk components is more than 99%. The presence of the core structure have a certain influence in the can's deformation and the powder's flow constraints and densification.