Hot Isostatic Compaction Research Articles

Features of VZhL21 Nickel-Base Superalloy Structure Formation During Selective Laser Melting, Vacuum Heat Treatment, and Hot Isostatic Compaction

This article considers features of the material structure of high-strength alloy VZhL21 obtained by selective laser melting (SLM) in different stages of its post-treatment. On the basis of analyzing the microstructure the so-called “process window” that is the interval of volumetric energy density for effective variation of (SLM) parameters during preparation of this material is determined. A study of synthesized VZhL21 alloy material is conducted by transmission microscopy with analysis of phase components and alloying element distribution within the volume of material. The efficiency of vacuum-heat and gasostatic treatment regimes is evaluated during crack healing. The structure of the material obtained is studied by light, scanning, and transmission microscopy after vacuum-heat, gasostatic, and heat treatment. The main structural components are determined by XPA.

Structure and short time degradation studies of sodium zirconium phosphate ceramics loaded with simulated fast breeder (FBR) waste

Sodium zirconium phosphate (NZP) ceramics have been prepared using conventional sintering and hot isostatic pressing (HIP) routes. The structure of NZP ceramics, prepared using the HIP route, has been compared with conventionally sintered NZP using a combination of X-ray diffraction (XRD) and (31P and 23Na) nuclear magnetic resonance (NMR) spectroscopy techniques. It is observed that NZP with no waste loading is aggressive toward the steel HIP-can during hot isostatic compaction and significant fraction of cations from the steel enter the ceramic material. Waste loaded NZP samples (10 wt% simulated FBR waste) show significantly low can-interaction and primary NZP phase is evident in this material. Upon exposure of can-interacted and waste loaded NZP to boiling water and steam, 31P NMR does not detect any major modifications in the network structure. However, the 23Na NMR spectra indicate migration of Na+ ions from the surface and possible re-crystallization. This is corroborated by Small-Angle Neutron Scattering (SANS) data and Scanning Electron Microscopy (SEM) measurements carried out on these samples.

Basic principles of baroelectric synthesis of Ti–Al3Ti metal–intermetallide laminate from Al–Ti foil package

A procedure for calculation of basic parameters of the baroelectric treatment of an Al–Al3Ti–Ti multilayer package in the synthesis of the Ti–Al3Ti monolithic metal–intermetallide laminate from a set of Al–Ti foils is proposed. Loading conditions at which the treatment time substantially decreases in comparison with hot isostatic compaction are shown.

Numerical Simulation of Hot Isostatic Pressing Process for the Manufacture of Parts Used in Biomechanics

This study is devoted to numerical modeling and simulation of the process of forming of metal powders by hot isostatic compaction (HIC) for the production of parts in biomechanics. A continuous model based on a visco plastic law is used to describe the process of densification HIP (hot isostatic pressing). The model was implemented in a finite element code developed under the platform FORTRAN POWER STATION. For numerical simulation, we considered a cylindrical die subjected to isostatic pressure and a temperature field. We study variations of different parameters: relative density and radial shrinkage. To validate the numerical model, the results are compared with experimental data.

Ni 59Zr 20Ti 16Si 5 bulk amorphous alloy obtained by mechanical alloying and powder consolidation

The possibility of fabrication of bulk amorphous Ni 59Zr 20Ti 16Si 5 (numbers indicate at.%) alloy by hot isostatic compaction of powders was investigated. The amorphous powders were obtained by ball milling of amorphous melt spun ribbon and by mechanical alloying of a mixture of powders of pure crystalline elements. The as-milled and hot-pressed samples were examined by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Fully amorphous bulk samples were successfully obtained by consolidating the ball milled amorphous ribbon, while compaction of mechanically alloyed powders resulted in partial crystallization of the alloy. Simultaneously, according to microscopy observations, the porosity of the last sample was lower than the one prepared from the ball milled ribbon. The obtained results testify the further optimisation of compaction parameters is needed.

The effect of processing on the elastic moduli of porous γ-TiAl

The effect of porosity on the dynamic elastic moduli of γ titanium aluminides samples that had undergone pressureless sintering or hot isostatic compaction was studied by ultrasonic sound wave velocity (SWV) measurements. The results indicate that the processing route affects the SWV and the elastic moduli. The latter depend not only on the density that was attained, but also on the temperature at which the consolidation was performed. The results indicate that the elastic moduli and sound wave velocities do not depend only on the extension of the interparticle interfaces present in the consolidated material. The usefulness of the SWV as a parameter for non-destructive evaluation of the Young's modulus of porous samples is presented.

Analysis of cold and hot isostatic compaction of spherical particles

Cold and hot isostatic compaction of monosized metal powders is analysed within the framework of viscoplastic theory for particles packed both in a regular and a random manner. The problem of local contact between spherical particles is analysed first by drawing upon recent detailed numerical studies of spherical indentation of power law plastic and creeping solids. The compaction process is then modelled as a self-similar contraction of unit (average) cells, in contrast to commonly used phenomenological assumptions, yielding a simple but rigorous relation between the densification density and centre-to-centre approach of adjacent powder particles. The resulting densification formulae are easy to apply and the influence of hardening and creep parameters appears in concise form. Predictions are compared with discriminating experimental data for a variety of different powder materials, both in the cold and a hot state, and the agreement is good for a relative density increase of up to 30%.

The influence of thermal expansion mismatch on the microstructure of Al 66Cr 9Ti 25-base composites

Al 3Ti is an attractive alternative structural material for high temperature applications. However, its tetragonal DO 22 structure displays very low ductility and fracture toughness at room temperature, severely limiting its potential applications. Researchers have found that a slightly more ductile cubic Ll 2 phase can be stabilized by alloying with transition metals. In order to enhance the usefulness of this material, prospective reinforcement materials (to form intermetallic matrix composites) have been examined for Al 66Cr 9Ti 25 (a cubic stabilized alloy). Elemental powders were used to prepare composites with metallic and ceramic reinforcements by reactive hot isostatic compaction. Experiments were also conducted to determine if secondary particle additions to the matrix could be used in conjunction with reactive hot isostatic pressing to reduce the thermal mismatch strain in composites. Tungsten and Al 2O 3 fibers were found to be the most compatible with Al 66Cr 9Ti 25, provided that tungsten particles were added to the matrix when tungsten fibers were used.

Influence of long-range order on tensile properties of Ni3Fe and Ni3Fe—Y2O3 composites

Ni3Fe is a compound that exhibits long-range ordering below 500 °C and a disordered structure above this temperature. Thus, Ni3Fe allows study of the effect of ordering on mechanical properties. This paper discusses the tensile properties of Ni3Fe produced via powder metallurgical routes. Some samples subsequently were densified by containerless hot isostatic compaction. Ni3Fe was consolidated with elemental nickel and iron powders that were solid state sintered. Composites of Ni3Fe with 5 vol. % Y2O3 were prepared by presintering cold isostatically pressed rods, followed by containerless hot isostatic pressing. The influence of Y2O3 particles on flow stresses of ordered and disordered Ni3Fe was determined. Ordering of Ni3Fe increased both strength and hardness with a small effect on ductility. For the Ni3Fe–Y2O3 composite, the increase in the strength in both ordered and disordered matrix conditions was accomplished by a large reduction in elongation.

Reactive sintering and reactive hot Isostatic Compaction of Niobium Aluminide NbAl3

NbAl3 has been synthesized from elemental powders by reactive sintering (RS) and reactive hot isostatic pressing (RHIP). Both processes involve a self-propagating exothermic reaction between the constituent powders to form an intermetallic compound. The RHIP approach uses simultaneous external pressurization to make a higher density product. This study focused on developing a method to use reactive synthesis to form high-density NbAl3 compacts. High RS and RHIP densities were possible with the appropriate raw materials and processing parameters. These include powder purity, particle sizes, degassing, heating rate, furnace temperature, and compaction pressures. Near full density was attained with RHIP, and up to 95 pct density was attained with RS.

System for the design of technological conditions for hot isostatic compaction of powders : A.A. Frolovet al. Poroshkovaya Metallurgiya, No 6, 1991, 12–17. (In Russian.)

System for the design of technological conditions for hot isostatic compaction of powders : A.A. Frolovet al. Poroshkovaya Metallurgiya, No 6, 1991, 12–17. (In Russian.)

Reactive sintering and reactive hot isostatic compaction of aluminide matrix composites

Reactive powder-processing techniques involve use of a transient liquid phase for the formation of a compound. Two variants of reactive synthesis have been successfully applied to the fabrication of aluminide matrix composites. In certain systems it is possible to react mixed elemental powders directly to form a nearly full density structure (such as Ni 3Al and NbAl 3). This approach is applicable to systems with sufficient adiabatic heating from the reaction exotherm to induce densification by liquid phase sintering. In systems with lower reaction enthalpies, an alternative involves the application of an external stress during the reaction. The two main variants illustrated here are hot isostatic compaction of mixed elemental powders (nickel + aluminum) or hot isostatic compaction of partially reacted powders (TiAl). From this base it is possible to identify the best processing approach based on the system thermodynamics.

Fabrication of intermetallic matrix composites

Abstract Research into the fabrication of intermetallic matrix composites is presented using the Ni 3 AlAl 2 O 3 system as the baseline. The approach combines reactive sintering, powder injection molding, and hot isostatic compaction to form an aligned fiber composite. The individual components to this process are described with example microstructures and mechanical properties. The initial successes and problems are described. The paper concludes with a description of the major remaining processing challenges in the fabrication of intermetallic matrix composites.

Elemental Powder Approaches to Ni3Al-Matrix Composites

Reactive sintering and hot isostatic compaction of mixed elemental powders have been combined to fabricate full density NiAl intermetallic-matrix composites. This process involves the formation of the matrix compound from its elemental constituents through an exothermic reaction. Dispersed ceramic phases inhibit direct consolidation, necessitating superposition of external pressure via hot isostatic compaction to obtain full density. The latter process is termed reactive hot isostatic pressing (RHIP). Because of its flexibility and low cost, this fabrication process merits attention as a means of preparing monolithic compounds and intermetallic-matrix composites.

A Study on Closest Packing of Gas-Atomized Steel Particles

In order to prepare closely packed mixtures for hot isostatic compaction, the flowing properties and blending conditions of gas-atomized steel powders were investigated. Being liable to size-segregation, spherical particles show a marked heterogeneity during the flow in a glass vessel.A magnetization treatment was tried to make the flowable steel powders attractive to each other, for varying their flow rates. Mixtures of attractive particles could be homogenized, when stirred in a certain range of flow rates.This enabled to prepare the closely packed mixtures without segregation, having apparent density of up to 75 per cent, whereas the values of untreated powders ranged from 63 to 65 per cent. The high density mixtures were compacted by hot isostatic pressing and the homogeneity of their structures was microscopically confirmed.

Hot Isostatic Compaction Using a Molton Glass as Pressure Transmission Media

Hot Isostatic Compaction Using a Molton Glass as Pressure Transmission Media

Hot Isostatic Compaction of Metallic Powder

Hot Isostatic Compaction of Metallic Powder

89. Dense, isotropic graphite fabricated by hot-isostatic compaction

89. Dense, isotropic graphite fabricated by hot-isostatic compaction