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Hot Isostatic Pressing (hot + isostatic_pressing)
Selected AbstractsHot Isostatic Pressing of Transparent Nd:YAG CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2009Sang-Ho Lee This paper demonstrates that fine-grained (2,3 ,m), transparent Nd:YAG can be achieved at SiO2 doping levels as low as 0.02 wt% by the sinter plus hot isostatic pressing (HIP) approach. Fine grain size is assured by sintering to 98% density, in order to limit grain growth, followed by HIP. Unlike dry-pressed samples, tape-cast samples were free of large, agglomerate-related pores after sintering, and thus high transparency (i.e., >80% transmission at 1064 nm) could be achieved by HIP at <1750°C along with lower silica levels, thereby avoiding conditions shown to cause exaggerated grain growth. Grain growth was substantially limited at lower SiO2 levels because silica is soluble in the YAG lattice up to ,0.02,0.1 wt% at 1750°C, thus allowing sintering and grain growth to occur by solid-state diffusional processes. In contrast, liquid phase enhanced densification and grain growth occur at ,0.08,0.14 wt% SiO2, especially at higher temperatures, because the SiO2 solubility limit is exceeded. [source] Hot Isostatic Pressing of Cubic Boron Nitride,Tungsten Carbide/Cobalt (cBN,WC/Co) Composites: Effect of cBN Particle Size and Some Processing Parameters on their Microstructure and PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007V. Martínez Cubic boron nitride (cBN)-cemented carbide composites have gained attraction over the last few years because of their potential uses as wear parts. The densification behavior of cBN,hard metal composites by glass encapsulation hot isostatic pressing,has been investigated. Composites with different cBN grades (from 0/0.5 to 6/12 ,m particle sizes) and cBN content (up to 50 vol%) were selected for this study. Near-full densification was obtained at temperatures between 1100° and 1200°C, and pressures between 150 and 200 MPa, respectively, while no phase transformation of cBN into the low-hardness hexagonal form has been detected by X-ray diffraction. The addition of cBN to the hard metal base material led to an increase of hardness, a significant increase of fracture toughness (KIC measured by Vickers indentation), and a moderate decrease of mechanical strength (determined by three-point bending). [source] Manufacturing Silicon Carbide Microrotors by Reactive Hot Isostatic Pressing within Micromachined Silicon MoldsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2002Jing-Feng Li A novel ceramic microfabrication process,based on the idea of silicon carbide (SiC) reaction sintering within a micromachined silicon mold,has been developed to produce a SiC microroter for miniaturized gas turbines. The new process involves the micromachining of silicon molds; filling the molds with powder mixtures of ,-SiC, graphite, and phenol resin; bonding the molds with an adhesive; reaction sintering by hot isostatic pressing (HIP); and the releasing of a reaction-sintered workpiece from the mold by wet etching. Using this process, we have successfully fabricated SiC microrotors with a diameter of 5 mm, whose complicated geometry was well transferred from the negative shape of the micromachined silicon mold. The reaction-HIPed SiC ceramics within Si molds showed reasonably good mechanical properties, which are comparable to those of the commercialized reaction-sintered SiC ceramics. [source] Al2O3/TiC Based Metal Cutting Tools by Microwave Sintering Followed by Hot Isostatic PressingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000Adrian Goldstein The feasibility of producing Al2O3/TiC metal cutting tools by fast microwave sintering followed by hot isostatic pressing was examined. Microwave heating profiles able to ensure near-full densification of Al2O3/TiC ceramic components were determined. Simple-shape specimens could be sintered to a bulk density of 97% theoretical density (TD) while in the case of tool-shaped ones maximal densification levels attained were somewhat lower, i.e., ,95% TD. Temperature uniformization,within the heating chamber,by using a particulate SiC susceptor noticeably reduced tool cracking propensity. Densification levels in the range acceptable for commercial tool manufacturing (,98% TD) were achieved by hot isostatic pressing of the microwave-sintered parts. The isostatically pressed parts exhibited a Vickers hardness Hv, 2000 kg/mm2 and a fracture toughness KIC, 4.3 MPa·m1/2. [source] Processing of ultra-high molecular weight polyethylene by hot isostatic pressing, and the effect of processing parameters on its microstructurePOLYMER ENGINEERING & SCIENCE, Issue 10 2004Rizwan M. Gul The processing techniques available for ultra-high molecular weight polyethylene (UHMWPE) do not lead to a homogeneous material. The processed material exhibits particle boundaries (fusion defects) reflecting the powder flakes of the virgin resin. Hot isostatic pressing has been used in this study as a possible technique to produce a homogeneous, defect-free material, and to study the effect of processing parameters on consolidation and other properties. The extent of consolidation was determined by optical microscopy using thin sections, and by scanning electron microscopy using cryofractured and solvent-etched specimens. Processing temperature is the most important variable affecting consolidation; fusion defects can be eliminated by increasing the processing temperature. This is sometimes accompanied by the appearance of spherulties; however, the degree of crystallinity, melting point, and density remain constant. DMA results show that the molecular weight between entanglements increases and the entanglement structure changes with an increase in processing temperature. Polym. Eng. Sci. 44:1848,1857, 2004. © 2004 Society of Plastics Engineers. [source] Hot Isostatic Pressing of Transparent Nd:YAG CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2009Sang-Ho Lee This paper demonstrates that fine-grained (2,3 ,m), transparent Nd:YAG can be achieved at SiO2 doping levels as low as 0.02 wt% by the sinter plus hot isostatic pressing (HIP) approach. Fine grain size is assured by sintering to 98% density, in order to limit grain growth, followed by HIP. Unlike dry-pressed samples, tape-cast samples were free of large, agglomerate-related pores after sintering, and thus high transparency (i.e., >80% transmission at 1064 nm) could be achieved by HIP at <1750°C along with lower silica levels, thereby avoiding conditions shown to cause exaggerated grain growth. Grain growth was substantially limited at lower SiO2 levels because silica is soluble in the YAG lattice up to ,0.02,0.1 wt% at 1750°C, thus allowing sintering and grain growth to occur by solid-state diffusional processes. In contrast, liquid phase enhanced densification and grain growth occur at ,0.08,0.14 wt% SiO2, especially at higher temperatures, because the SiO2 solubility limit is exceeded. [source] Hot Isostatic Pressing of Cubic Boron Nitride,Tungsten Carbide/Cobalt (cBN,WC/Co) Composites: Effect of cBN Particle Size and Some Processing Parameters on their Microstructure and PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007V. Martínez Cubic boron nitride (cBN)-cemented carbide composites have gained attraction over the last few years because of their potential uses as wear parts. The densification behavior of cBN,hard metal composites by glass encapsulation hot isostatic pressing,has been investigated. Composites with different cBN grades (from 0/0.5 to 6/12 ,m particle sizes) and cBN content (up to 50 vol%) were selected for this study. Near-full densification was obtained at temperatures between 1100° and 1200°C, and pressures between 150 and 200 MPa, respectively, while no phase transformation of cBN into the low-hardness hexagonal form has been detected by X-ray diffraction. The addition of cBN to the hard metal base material led to an increase of hardness, a significant increase of fracture toughness (KIC measured by Vickers indentation), and a moderate decrease of mechanical strength (determined by three-point bending). [source] Manufacturing Silicon Carbide Microrotors by Reactive Hot Isostatic Pressing within Micromachined Silicon MoldsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2002Jing-Feng Li A novel ceramic microfabrication process,based on the idea of silicon carbide (SiC) reaction sintering within a micromachined silicon mold,has been developed to produce a SiC microroter for miniaturized gas turbines. The new process involves the micromachining of silicon molds; filling the molds with powder mixtures of ,-SiC, graphite, and phenol resin; bonding the molds with an adhesive; reaction sintering by hot isostatic pressing (HIP); and the releasing of a reaction-sintered workpiece from the mold by wet etching. Using this process, we have successfully fabricated SiC microrotors with a diameter of 5 mm, whose complicated geometry was well transferred from the negative shape of the micromachined silicon mold. The reaction-HIPed SiC ceramics within Si molds showed reasonably good mechanical properties, which are comparable to those of the commercialized reaction-sintered SiC ceramics. [source] Fabrication of Graded Nickel,Alumina Composites with a Thermal-Behavior-Matching ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2000Andrew N. Winter Composites of nickel and Al2O3 with compositionally graded microstructures were fabricated from powders through an empirically determined thermal-behavior-matching process that was designed to minimize processing-induced stresses. Compositions ranged from pure Al2O3 to pure nickel. Specimen geometries included round disks 25 mm in diameter and 5,25 mm thick, as well as rectangular bars 25 mm × 25 mm in cross section and 75 mm long. Several different gradients were produced, including samples with single interlayers. Compacts were formed by cold uniaxial pressing in a die, followed by consolidation through sintering at 1 atm or hot isostatic pressing. Several different particle sizes of nickel and Al2O3 comprised the composite interlayers. The compaction behavior, sintering start temperature, sintering rate, and total linear shrinkage of each composition were evaluated. Careful data analysis, coupled with sintering theory, led to a layer configuration with matched green density and sintering behavior. Thermomechanically matched layers allowed large, crack-free, graded composites to be produced. [source] Al2O3/TiC Based Metal Cutting Tools by Microwave Sintering Followed by Hot Isostatic PressingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000Adrian Goldstein The feasibility of producing Al2O3/TiC metal cutting tools by fast microwave sintering followed by hot isostatic pressing was examined. Microwave heating profiles able to ensure near-full densification of Al2O3/TiC ceramic components were determined. Simple-shape specimens could be sintered to a bulk density of 97% theoretical density (TD) while in the case of tool-shaped ones maximal densification levels attained were somewhat lower, i.e., ,95% TD. Temperature uniformization,within the heating chamber,by using a particulate SiC susceptor noticeably reduced tool cracking propensity. Densification levels in the range acceptable for commercial tool manufacturing (,98% TD) were achieved by hot isostatic pressing of the microwave-sintered parts. The isostatically pressed parts exhibited a Vickers hardness Hv, 2000 kg/mm2 and a fracture toughness KIC, 4.3 MPa·m1/2. [source] Transparent Polycrystalline Alumina Ceramic with Sub-Micrometre Microstructure by Means of Electrophoretic DepositionMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2006A. Braun Abstract The optical quality attainable in coarse-grained polycrystalline alumina is severely limited by grain-boundary scattering, which is inherent to non-cubic materials. The optical properties of sub-micrometre polycrystalline alumina are of growing interest triggered by the fact that a decrease in the grain sizes of the final sintered material yields an improvement in the optical quality while the scattering mechanism changes as the grain size becomes comparable with the wavelength of light. To achieve transparent alumina ceramics with a fine-grained microstructure, however, porosity and other defects must be avoided. This necessitates the optimization of processing and sintering procedures. Electrophoretic deposition (EPD) is a colloidal process in which ceramic bodies are directly shaped from a stable suspension by application of an electric field. Electrophoretic deposition enables the formation of homogeneous, uniform green microstructures with high density, which can be sintered to transparency. It is a simple and precise technique to synthesize not only monoliths, but also composites with complex geometries [1]. Alumina green bodies were deposited from stabilized aqueous suspensions with and without doping. Green alumina compacts were evaluated based on their pore size distribution and density. Densification behaviour was characterized by dilatometric studies conducted at constant heating rate. Samples were sintered at different temperatures with subsequent post-densification by hot isostatic pressing. Transparency was evaluated by means of spectroscopic measurements. The measured in-line transmission of the samples at 645 nm was more than 50,% and that is 58,% of the value of sapphire. The influence of dopings on transparency was investigated. The mechanical properties of the samples were tested. [source] Processing of ultra-high molecular weight polyethylene by hot isostatic pressing, and the effect of processing parameters on its microstructurePOLYMER ENGINEERING & SCIENCE, Issue 10 2004Rizwan M. Gul The processing techniques available for ultra-high molecular weight polyethylene (UHMWPE) do not lead to a homogeneous material. The processed material exhibits particle boundaries (fusion defects) reflecting the powder flakes of the virgin resin. Hot isostatic pressing has been used in this study as a possible technique to produce a homogeneous, defect-free material, and to study the effect of processing parameters on consolidation and other properties. The extent of consolidation was determined by optical microscopy using thin sections, and by scanning electron microscopy using cryofractured and solvent-etched specimens. Processing temperature is the most important variable affecting consolidation; fusion defects can be eliminated by increasing the processing temperature. This is sometimes accompanied by the appearance of spherulties; however, the degree of crystallinity, melting point, and density remain constant. DMA results show that the molecular weight between entanglements increases and the entanglement structure changes with an increase in processing temperature. Polym. Eng. Sci. 44:1848,1857, 2004. © 2004 Society of Plastics Engineers. [source] | ||||||||||