| Inconel625is a typical nickel-based superalloy, widely used in the aerospace andchemical industries. It was manufactured by casting and forging traditional process in thepast. There are disadvantages of macroscopic composition segregation by casting and lowmaterial utilization by forging, while it is manufactured by powder hot isostatic pressing(HIP), we can get that Inconel625alloy has excellent properties comparable with theforgings, and material utilization is significantly improved, besides the complex parts canbe overall near-net formed. Therefore, powder hot isostatic pressing near-net shaping has adistinct advantage in the manufacture of key components such as the high thrust-to-weightratio aero-engine turbine disk. However, prior particle boundaries (PPB) in Inconel625alloy are easily formed during hot isostatic pressing, which adversely affect theperformance, and it can be effectively eliminated by reasonable solution heat treatment. Thehot isostatic pressing and solution heat treatment of Inconel625alloy were studied little athome and abroad currently, and there was no in-depth study on the microstructure andproperties of hot isostatic pressed Inconel625alloy.Inconel625alloy was formed by hot isostatic pressing with five groups of differenttemperatures and pressure, and the microstructure and properties of the alloy formed by theoptimum process were characterized and analysed. Besides, the microstructure andproperties of the alloy through solution treatment with several groups of differenttemperatures and holding time were also characterized, compared and analysed.The results show as follow:(1) As the temperature and pressure during hot isostaticpressing rise, the Inconel625alloy powders gradually achieve densification molding.1050℃/120MPa/3h are the optimum hot isostatic pressing parameters, the alloy formed atwhich was totally densified and its matrix structure was austenite γ phase whose sizes arecomparable with the powder particles.(2) The Inconel625alloy formed by the optimum hot isostatic pressing has uniform structure and no significant component segregation, but thereremains a great quantity of PPBs composed of chain-like carbides. Its yield strength andtensile strength at ambient temperature are499.12MPa and983.38MPa, and its elongationis26.29%; meanwhile its yield strength and tensile strength at650℃high temperature are356.00MPa and761.51MPa, and its elongation is27.43%. The strength achieves orprecedes the level of the forgings in ASTM and China Aviation Materials Manual. However,the ductility both at ambient temperature and650℃is not very good because of the PPBs.(3) The PPBs can be effectively eliminated by reasonable solution treatment so that themicrostructure and comprehensive mechanical properties are improved. The carbidesdissolved sufficiently as the solution treatment temperature rises, meanwhile the strengthand hardness descend a little while the ductility is improved notably. The ductility is thebest at1100℃because of32.8%elongation. However, when the temperature is too highsuch as1200℃, the hardness, strength and ductility all descend fiercely because of thatpart of carbides grow up and burnt structure appears. The ductility becomes better andbetter because of the solution of carbides and the disappearance of PPBs with theprolongation of the solution holding time. The comprehensive properties are the best for30min holding time. However, when the holding time is too long such as40~50min, thestrength descends obviously. In conclusion,1100℃/30min/water cooling are the optimumsolution treatment parameters, the hardness of the alloy treated by which descends4.9%,the strength at ambient temperature changes little, and the elongation increases25.8%.There are a large number of small-scale dimples in tensile fracture, which shows thefracture mechanism is toughness fracture, and this ensures a good ductility. |
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