Abstract: Dendritic arms spacings of FGH95 and Rene'95 atomized powder for different mesh size were measured. Cooling rate (Ṫ) > local solidification time(tf), thermal gradient (G), and growth rate (R) were calculated.It is shown that as local solidification time is 10-1-10-2s,cooling rate of two powders inside the range of -60-+320 mesh is 103-104℃/s.The cooling rate and O/R ratio inerease with decreasing particle size and dendrite structure of powder particle correspondly changes into cellular structure.It seems that the morphology of MC carbibe in powder particle does not depend only on O/R ratio.
Abstract: Microstructures of argon-atomized FGH95 and imported Rene'95 superalloy powders after heat treatment were studied.It is shown that homogenization of dendritic microstructure is more difficult to complete than that of cellular mie-rostructure. The dendritic microstructure can be homogenized during heat treatment at 1140℃ for 3h. The solution temperature of FGH95 powder is lower than that of Rene'95.
Abstract: Particle shape,surface morphology and microstructure of skin layers and adhering satellites were studied by using optical and scanning electron microscopy.It was observed that as the powder size decreases, the frequency of occurrence of both satellites and skin layers diminish and the shape of powder approaches that of a sphere.There are two kinds of microstructure on adhering locations,i.e. one is with marked boundary and the other is without boundary.
Abstract: The precipitation phases present in argon-atomized FGH95 superalloy powders were studied by X-ray diffraction, transmission electron microscopy and X-ray energy dispersive spectra techniques. The major precipitate Phase in the interior of the powder particles is identified as MC-type carbides containing Nb and Ti with some Cr,Ni, Mo and W.The morphology of MC-type carbides may be related to the composition of the alloy and the condition of its solidification.Minor Phases,such as Laves phase, primary γ' phase and boride phase are also present.
Abstract: The problem of previour powder-particle boundary (PPB) was studied in a nickel-base P/M superalloy FGH95. The results indicate that carbides begin to form on the powder surface while atomization and continue to precipitate and grow into continous networks during HIP-consolidation. As a result of complex composition of carbides the different type carbides interact probably. The amount of PPB precipitation increases significantly during post-HIP heat treatment. The formation of PPB carbides is related to the amount of residual oxygen or oxygen contamination in alloy.
Abstract: The second dendrite arm spacings were measured by the method of stereolog-ical metallography method. The cooling rate is determined by the Newton's Cooling Law, and the time required for entirely solidification of powder particles is calculated as well. The second dendrite arm space of Rene'95 alloy powder is related with the particle size, cooling rate、solidifying rate and the time needed for solidification. The relationships are represented as d=0.242D0.489, d=102.9v-0.488, d=2.47 (dε/dt)-0.492, and d=39.28tk0.245. The results of the study made it clear that the commom equations of casting, i, e, d=av-n, d=btn, where n is between l/3-l/2, can be applied to the olidification process of argon-atomised Rene'95 alloy powder particles.
Abstract: Water Elutriation method was applid to determin the content of ceramic inclusions in P/M Rene'95 powder paticles quantitatively. The study proved that is quite adequate for the analysis of ceramic inclusions in superalloy powders, which can vary either in size or in morphology. Several parameters concerning with the ceramic inclusions were determined. Furthermore, the compositions and the morphology of the ceramic inclusions are discussed as well.
Abstract: The percentage of porous particles in argon-atomised FGH95 alloy powder and the relationship between average size of pores and the particles size were studied by real density measureng method, stereological metalography and Image Analyser. The study was led to the conclusion that as the particles size increases,both the percentage of porous particles and the average size of pores become larger. Most of the pores are equaxial or sphere like.And the larger the particle size is, the more spherical the shapes of the pores are. The internal porosity of FGH95 alloy powder determined by density method deviates a little from that determined by other two methods. The change regularity obtained by the above three methods is the same.The average size of the porosity measured by optical microscope and by Image Analyzer is also the same.
Abstract: FGH95 alloy powder produced by argon atomisation and Rene'95 powder have been investigated by using optical microscope, TEM, SEM, EDAX and AES. The morphology and microstructure of powder particles were observed and the composition of the particle surface was determined. The comparison between alloy powder particles was made.
Abstract: By means of TEM, TEDAX and AES the chemical composition and precipitates on particle surface and at the primary particle/particle boundaries of HIPed billet have been investigated. Experimental results show that the particle surface of powders produced by Ar atomisation is enriched with S、C、Ti、O and TiC particles also precipitate on the surface. After hot isostatic pressing, the carbides distributed around the primary-particle boundaries are niobium ri-ched (Nb, Ti, Mo) C phase, S and O concentration drastically decreases at the primary-particle boundaries, and a small amount of P segregate to the primary-particle boundaries during hot isostatic pressing.
Abstract: The effect of structural defects on the formation of quench cracks in a Nickel-base P/M superalloy was studied. The serious quench crack is due to the presence of rich-oxygen layer on the.Particle surface and the formation of PPB carbides destroying the continuity of the alloy and promoting fracture along the previous particle boundaries. The slight quench crack is due to the precipitation in a coarse form at the grain boundaries. The coarseγ' precipitates are surrounded by zones depleted Al,Ti froming oxide layers which promote the fracture path along the grain boundaries. The major reason of the formation of quench cracks is the contamination of oxygen in the early processing or unsuitable quench cooling rate during heat treatment.
Abstract: Microstructures of P/M superalloy FGH95 in the HIP'ed and HIP'ed plus heat treated condition are investigated with optical microscopy, TEM, and X-ray diffraction. The results show that r' MC,M23C6 phases are present in samples after both HIP'ed and HIP'ed plus heat treated condition.Al-rich and Zr-rich oxides are found at the primary particle boundaries.
Abstract: FOH95 alloy has been put into use for more than ten years.The present work has studied the microstructure of FGH95 alloy after HIPing and heat treatment at different temperatures. The particle surface segregation and surface structure were investigated by using AES and ESCA. The changes of all-microstructure during HIPing were investigated by microscope, SEM, TEM and particularly by a detailed observationof STEM on extraction replica and metallic thin foils. It wss evidenced that when the powder was HIPed at above 1050℃ MC carbides precipitated discretely at ppb, and the space between two particles is much greater than the size of these carbides. After aging treatment a lot of MC carbides precipitated at ppb would be converted to film like M23C6 carbides, which is semi-continuously distributed at the ppb.The solvus temperature of γ'-phase was found to be affected by the HIPing pressure.The results of AES and ESCA analysis showed that there were segregation elements such as O, C, Cr, Ti and S on the powder particle surface, and that the particle surfaces were partialy oxidized.
Abstract: Ceramic inclusions in as-HIPed and HIP+forged P/M superalloy specimens were studied by stereological metalography method quantitatively and by Electron Probe Microanalyser qualitatively. The ceramic inclusions in FGH95 superalloy were compared with those in Rene'95 superalloy.The present results show that the ceramic inclusions in FGH95 superalloy consists of mainly Al2O3 and it's complex oxides with SiO2. different from that in Rene'95 alloy, which are complex oxides of SiO2 with MgO and AlSiOa with MgO.The amount of inclusions in FGH95 superalloy is about three times as much as that in Rene'95 superalloy, and the inclusions in FGH95 superalloy are also coarser than those in Rene'95 alloy.
Abstract: The densities of HIPed compact of Rene'95 P/M superalloy were measured before and after the solution heat treatment to study the formation of TIP, and it's changes during heat treatment. The present work has found that the amount of TIP increases with the increase of temperature and the time of heating.The temperature and the time of the heat treatment are two important factors for the specification of TIP in powder metallurgy superalloys.
Abstract: The influences of mild steel container on Hot Isostatic Pressed powder metallurgy superalloys is studied in this paper. It is concluded that there are some interaction of the mild steel on the hot pressed compact.The diffusiou of alloy elements will result in forming such zones which may be poor in alloy elements or rich in iron on the surface layer of the compact. The thickness of this layer varies with HIPing temperature and HIPing time. Meanwhile non-γ' phase area will form in the surface layer, as the consequence of the iuteraction. An equation was obtained to describe the relationship between the diffusion depth and the time at different HIPing temperature.The hardness from the surface layer to the core of the specimen was measured as well.The influence of carbon content of the mild steel was also discussed.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
