HIP Process Research Articles

HIP processing of titanium aluminide from blended elemental powders: P. Lee-Sullivan, J. Materials Processing Technology, Vol 38, No 1–2, 1993, 483–489

HIP processing of titanium aluminide from blended elemental powders: P. Lee-Sullivan, J. Materials Processing Technology, Vol 38, No 1–2, 1993, 483–489

Joining of Ceramics of Different Biofunction by Hot Isostatic Pressing

Monolithic zirconia (Z) and zirconia‐hydroxyapatite (Z/HA) composites were joined by cold isostatic pressing (CIP at 300 MPa) and subsequently by glass‐encapsulated hot isostatic pressing (HIP at 1225°C, 1 h and 200 MPa). The physical and mechanical properties of the materials were measured. The fracture surface was studied using a light microscope. The results indicate a strength level of the joint similar to that of the corresponding composite material (Z/HA), 845 and 860 MPa, respectively. Similar experiments with monolithic alumina (A) and alumina‐hydroxyapatite (A/HA) were carried out without success. Cracking occurred in the joint area during the cold isostatic pressing process. It seems that ceramics with high green strength and similar green density are essential when joining ceramics by combined CIP and HIP processes.

Si<sub>3</sub>N<sub>4</sub>-SiC Composite Consolidated by Post-HIPing Process

Si3N4-SiC particle composites constaining up to 30wt% SiC were sintered to a neary full density using gas pressure sintering and HIPing process (post-HIPing). Fine SiC powder with an average particle size of about 0.03μm, and Y2O3 as sintering additive were used. Si3N4-30wt% SiC sintered composite with a strength of about 700MPa at 1400°C was obtained by post-HIPing.

Microstructural Control of Ni–Zn Ferrites for Thin Film Heads

The microstructural changes during sintering of Ni-Zn ferrites used as the substrate for thin film magnetic recording heads have been studied by SEM, XRD and XPS. Any precipitates were not observed in the specimen air-sintered and furnace-cooled from 1423 K. ZnO precipitates, however, were observed at the grain boundaries, especially at the grain boundary triple points of the specimen furnace-cooled from 1453 K. While the above-mentioned ZnO precipitates were not observed on the specimen sintered in oxygen, the grain coarsening was observed in this case, with residual pores being trapped inside the grains. The existence of Ni 3+ ion was detected by XPS on the specimen prepared by HIP process, where the ratio of Ni 3+ /(Ni 2+ +Ni 3+ ) was confirmed to be about 3%...

Hip process quality based on combination of numerical and stochastic models

For the first time, perturbation bounds including componentwise perturbation bounds for the block LU factorization have been provided by Dopico and Molera (2005) [5]. In this paper, componentwise error analysis is presented for computing the block LU factorization of nonsingular totally nonnegative matrices. We present a componentwise bound on the equivalent perturbation for the computed block LU factorization. Consequently, combining with the componentwise perturbation results we derive componentwise forward error bounds for the computed block factors.

Intelligent processing in hot isostatic pressing: R.J. Schaefer, (National Inst of Standards and Technology, Gaithersburg, Maryland, USA), Int. J. Powder Metallurgy, Vol 28, No 2, 1992, 161–173

Successful hot isostatic pressing of metal or intermetallic powders requires that the product meet many goals with respect to shape, density, microstructure, and cost. The development of sensors that can detect sample characteristics during HIP consolidation and process models that can predict how the sample characteristics will respond to changes in environment raises the possibility of active control based on these

An Analysis of Void Deformation Caused by Power Law Creep and Diffusion Enhanced by Mechanical Stress in HIP Process

A dominant deformation mechanism in an isostatic pressure sintering process of a powder compact is known as power law creep. The deformation of a pore was predicted from the existing stress analysis based on power law creep assuming a hollow sphere and a hollow cylinder. The deformation at high temperature (T> 0.4 Tm) involves both power law creep and diffusion enhanced by mechanical stress. The analysis performed by previous investigators included only the deformation caused by power law creep. The analysis in this paper is considering for both the deformation caused by power law creep and diffusion in the final stage of the HIP process for a hollow sphere and hollow cylinder models. The contribution of the diffusion mechanism to the total densification is investigated. The experimental results published for CoO are compared with the analytical result for power law creep only and for power law creep and diffusion. The results show that the effect of diffusion on the total densification is insignificant for densities of the order of 80 percent of theoretical at low applied pressure, and for a small vacancy diffusion coefficient (Dv). However, the contribution of diffusion is increased in the high densification region (ρ>0.95), with high applied stress and high Dv. It is concluded that the diffusion mechanism enhances the densification and its rate in the final stage of HIP process.

薄膜磁気ヘッド用Ni-Znフェライトの組織制御

In this experiment, the microstructural changes during sintering of Ni-Zn ferrites used as the substrate for magnetic recording heads of thin films have been studied by SEM, XRD and XPS. The results obtained are sammarized as follows.(1) No precipitates were recognized on the specimen furnace-cooled from 1423 K during sintering in air. ZnO precipitates, however, were observed at the grain boundary, especially at the triple point of the specimen furnace-cooled from 1453 K. These precipitates have been elongated along grain boundaries of the specimen furnace-cooled from 1453 K after holding at this temperature for 10.8 ks.(2) While the above mentioned ZnO precipitates were not observed on the specimen sintered in O2 atmosphere, the grain coarsening was observed and the residual pores were also recognized inside the grain.(3) The existence of Ni3+ ion was detected by XPS on the specimen prepared by HIP process at 1373 K for 18 ks under 120 MPa after sintering in air at 1453 K for 10.8 ks, where the ratio of Ni3+/(Ni2++Ni3+) was confirmed to be 3%.

メカニカルアロイングにより作製したアモルファスCoNbZr粉末のHIP固化成形

A novel HIP processing of mechanically alloyed(MA) amorphous powder is developed, based on the densification via viscous flow mechanism, with which it is possible to obtain a fully dense amorphous compact of large scale. This study describes the evaluation of viscous flow in a thermal mechanical analyzer (TMA) and the optimization of HIP variables, time, temperature, pressure and heating rate for a nearly full densification of MA amorphous Co79.5Nb15Zr5.5 powder.The pre-compacted compressive sample of amorphous Co79.5Nb15Zr5.5 shows a drastic plastic displacement after thermal shrinkage in a constant heating rate experiment far below the temperature at the onset of crystallization(Tx). An analysis of the TMA curve for a porous amorphous compact permits us to derive the displacement rate and the viscosity. The temperature dependence of the newtonian viscosity(η) is fairly well expressed by an Arrhenius typed relation of η=η0 exp (221 kJ·mol−1/kT) within the range of the experiment in this study. The well-defined glass temperature(Tg) shows a constancy for heating rates above 1.7×10−1 K·s−1, but a great increase due to structural relaxation below 8.3×10−2 K·s−1.HIP cmpaction of MA amorphous powder in vacuumed can in a temperature range, Tg<T<Tx under a pressure of 196 MPa makes it possible to obtain a high density amorphous product with a diameter of 24 mm at the nearly maximum in our laboratory HIP apparatus. An increase in holding time and/or temperature leads to an increase in relative density of the amorphous HIP compact, approaching to theoretical one. These increases are in good agreement with a HIP map which is constructed based on newtonian viscous flow mechanism with an Arrhenius equation with an increased η0 for MA amorphous powder subjected to extensive structural relaxation.The compressive strength(σF) for the amorphous HIP compact of Co79.5Nb15Zr5.5 greatly increases with decreasing porosity(Po). A power law of compressive strength is derived as σF=BP−0.5o.

Ceramic cathodes for arc-physical vapour deposition: development and application

Abstract Cathodes for reactive and non-reactive d.c.-arc physical vapour deposition were developed using sintering and high-pressure HIP techniques and commercial TiB 2 powders. High-purity basic materials were doped with traces of various additives to improve HIP processing behaviour, resulting in pycnometric density, thermal and electrical conductivity beneficial to arc evaporation. Examinations of thermal and electrical properties, density and homogeneity were carried out on cathode materials, which were previously tested in arc-evaporation equipment with respect to various parameters (particle emission, thermal and electrical behaviour, spot movement characteristics, bias current, behaviour under reactive and non-reactive gas atmospheres of various pressures). Tests revealed a dependence between physical properties of cathode material and behaviour during evaporation testing, with good results for thermally and electrically conductive materials of high density. Furthermore, coatings (reactive Ti-B-N as well as non-reactive Ti-B) were deposited onto several substrates with cathodes that showed good results in previous evaluation tests. The coatings were analysed by measuring the deposition rate, microhardness, critical scratch load, and structural parameters (using X-ray diffractometry as well as REM). The dominant coating properties were high hardness and low droplet yield at favourable deposition characteristics.

Preparation of YBa 2Cu 4O 8 by a seeding method at ambient pressure

A seeding method was applied to the processing method of YBa 2Cu 4O 8 superconducting oxide (124 phase). Seed of the 124 phase was prepared by the HIP process. Seed with 25 wt.% was mixed with the matrix oxide prepared by decomposition of nitric salt. They were pressed and fired at 850°C under oxygen gas flow (1 atm of oxygen partial pressure). After repeating the firing, the 124 single phase was obtained. The sample of this 124 phase exhibited superconductivity at onset temperature of 82 K and zero resistive point at 76 K. From the matrix oxide (unseeded), however, the 124 phase could not be formed under the same conditions.

Numerical modelling of HIP: Influence of operating parameters and rheology of the porous material: C. Dellis, et al, (Institut Mecanique de Grenoble, Grenoble, France)

Hot isostatic pressing (HIPing) is a promising near net-shape manufacturing technology that can be employed for fabrication of complex parts out of metal powders. Design of tooling/canister that allows net-shape HIPing is still based on expensive experimental try-outs and subsequent iterations to modify the initial canister geometry. An auspicious alternative approach is finite element (FE) simulation. However, the FE results are strongly dependant on the implemented powder metal constitutive model. The current research shed the light on finite element analysis of HIPing process, based on steel 316L powder, using three different constitutive models namely; CAM-Clay, modified Drucker-Prager and modified Drucker-Prager with creep. Comparison with experimentally deformed final geometry and densification history of the HIPed material were carried out. Discrepancies in predicted final geometry dimensions were ranging from 1% to 6.34% compared to experimental trials. Drucker-Prager with creep constitutive model showed the highest accuracy in final geometry predictions with relative error of 1.5∼4.8%.

Near net shape HIP processing of Ti alloys using ceramic moulding: D. Brenet, F. Bernier, (C.E.A., Cerem, France)

Near net shape HIP processing of Ti alloys using ceramic moulding: D. Brenet, F. Bernier, (C.E.A., Cerem, France)

In-situ diagnostic techniques for improved HIP processing and quality control: D. Stover, et al, (Institut fur Angewandt Werkstofforschung, Forschungzentrum Julich GmbH, Julich, Germany)

In-situ diagnostic techniques for improved HIP processing and quality control: D. Stover, et al, (Institut fur Angewandt Werkstofforschung, Forschungzentrum Julich GmbH, Julich, Germany)

Effect of Isostatic GAS Pressure on Optical Quality of MgAl2O4 Spinel

ABSTRACTOptical transparent MgAl2O4 spinel is obtained by processing with high gas pressure to eliminate or reduce the residual pores. Both hot–pressed and sintered specimens are post–treated by the high argon hipping process here. The densities of all the specimens before hipping are over 99% theoretical density. In the high gas pressure process, the pressure ranges from 2000 to 30000psi at 1500°C for 2hrs. The transmittance from visible to IR are measured before and after gas pressure treatment. The transparency from visible to IR increases significantly with the HIP process. When applied pressure less than 6000psi, bulk density is proportional to the logarithm of the pressure and the logarithm of the absorption coefficient is proportional to the porosity. Bimodal grain–size distribution exists in the sintered and hipped specimens but is not observed in the uniaxial–hot–pressed–only samples. XRD analysis indicates the width of the diffraction peaks in the HIP specimens is less than that in UAHP specimens. The result illustrates the HIP process improves the spinel crystallinity.

Effect of Relative Density on a Compressive Deformation Rate in Chromium Carbide Composite(Cr3C2+Cr7C3)and the Reliability in the Strength.

The effect of relative density on a compressive deformation rate in chromium carbide composite (Cr3C2+Cr7C3) and the reliability in the strength was investigated. A chromium carbide sintered compact with a carbon content of 13.1wt% was fabricated from the high purity Cr3C2 powder with a particle size below 1μm. After being presintered at 1673-1773 K for 3000 sunder a vacuum of 0.13 Pa, the green compact was pressed isostatically at 150 MPa at 1623K for 3600s. The deformation rate in the composite with a lower relative density increases under a high compressive strength at an elevated temperature. But that with a higher relative density above 98% is hardly influenced by a stress. A HIP process is significantly effective in increasing in the density of the composite. The composite with a Weible parameter of 16.8 can be produced with a deflection of±15% in 2S/σm by the HIP.

HIP of Powder Mixtures

ABSTRACTModels of pressure-sintering and consolidation (such as that found in the HIP process) often assume a uniform spherical powder. However, it is known that use of mixtures, containing particles of differing composition and/or size, alters the initial powder packing and subseguent HIPing behavior. We have experimentally investigated these effects using the simplest form of mixture; a bi-modal powder with various size ratios and particle fractions. Packing experiments confirm the existence of “optimum” packing fractions for which the density is maximized over both monosized and the as-received (continuously distributed) powders. During HIPing these powder mixes remain relatively more dense than monosize packings. The consolidation of composite powder mixtures as well as microstructural evolution during HIP are also discussed. Results are compared with those predicted by modeling.

Corrosion resistant bimetallic pipe manufactured by HIP and hot extrusion(HHE) process.

Corrosion resistant bimetallic pipe manufactured by HIP and hot extrusion(HHE) process.

Transmission Optical Properties of Polycrystalline Alumina with Submicron Grains

Translucent alumina ceramics with extremely high in-line optical transmittance to visible light and light mechanical strength were produced by applying HIP process to a sample which was densified at a relatively low temperature after injection molding. Measurements of bulk density and average grain size, X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS) analysis, and SEM and TEM observations were conducted

Advanced surface engineering by hipping

Aluminide coatings produced by an ion vapour deposition and hipping process show certain technical advantages over those produced by conventional pack techniques. Examples are given of aluminide coatings produced on nickel based superalloys.