Research On Pseudo Hot Isostatic Pressing Of Spray Formed Bimetal Composite Plate

Compared with the traditional casting process,spray deposition technology can not only produce new high-performance metal and metal matrix composite materials,and the microstructure of the spray deposited billets is fine.The comprehensive performance of materials which are greatly enhanced by spray deposition technology is better than those formed by the traditional casting process.But the spray-deposited billet always contains a small amount of pores resulting in poor performance.Thus,the appropriate densification is very necessary for a satisfactory comprehensive performance.However,it is difficult to realize the densification of spray deposited plates by using conventional densification methods,such as hot extrusion,forging,rolling and wedge pressure technology,due to the limitation of the pressure device or the destruction of the component distribution after being compressed.This paper presents a new method of densification – pseudo hot isostatic pressing.Compared to the normal density process,it has the advantage of simple operation and low cost,and the effect of densification is good.This paper carries out the basic research on bimetal composite plate prepared by spray deposition technique using pseudo hot isostatic pressing process for subsequent densification.Based on the generalized plastic mechanics model,the material model suitable for the deformation of powder medium is established,that is,the modified Drucker-Prager Cap model and the hardening curve.The relative density of the spray material is kept between 80% and 90%.Therefore,the bimetal composite plates prepared by the spray deposition technique in this paper are classified as porous materials,the porous material model is used in the simulation process.The finite element simulation software ABAQUS was used to simulate the pseudo hot isostatic pressing process and analyze structural parameters: Powder medium diameter ratio and different pressing methods,analyze the effect of stress-strain and density distribution on the compression process of cylindrical compacts.The results show that the powder height is 100 mm and use two-way compression method,the densification of the blank is better.The influence of the process parameters on the densification process of the blank is simulated and analyzed.The stress strain and density variation of the plates under different temperature and different pressure are compared.so as to get the best parameters of pseudo hot isostatic pressing process.The results show that the process parameters using a temperature of 380 ? and a pressure of 150 MP,the densification of the spray blank is substantially dense.The overall density of the simulation results can reach about 97.5%.In order to compare with simulation results for verification analysis,the cylindrical specimens taken from the spray deposited composite plate were densified by the pseudo hot isostatic pressing process.The results show that the process parameters using the powder height of 100 mm,two-way compression,a temperature of 380 ? and a pressure of 150 MP,the blank structure of the blank is basically closed,and the density can reach about 99%.Hardness value is effectively improved,and the hardness value is increased from 59.9 kgf / mm~2 to 84.5 kgf / mm~2 before pressing.The experimental results are in good agreement with the simulated results.