Fabrication of NiTi and NiTi-nano Al₂O₃ composites by powder metallurgy methods: Comparison of hot isostatic pressing and spark plasma sintering techniques

Farvizi, M.,Javan, M. Kahkhaei,Akbarpour, M.R.,Kim, H.S. Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.13

<P><B>Abstract</B></P> <P>To escape the detrimental effect of NiTi matrix decomposition on hot-isostatic-pressing (HIP)-processed NiTi-nano alumina composites, which leads to the formation of NiTi<SUB>2</SUB>/Ni<SUB>3</SUB>Ti intermetallics; in this study, spark plasma sintering (SPS) was utilized to restrict this phenomenon in NiTi and NiTi-6 wt% nano alumina composites. After optimization of the SPS processing conditions, the microstructural aspects of the SPS and HIP-consolidated samples were compared. According to X-ray diffraction analysis, the SPS-processed composites contained more B2-NiTi phase than the HIP-processed samples did. This is because of lower NiTi matrix decomposition due to formation of NiTi<SUB>2</SUB>/Ni<SUB>3</SUB>Ti phases. Scanning electron microscopy studies revealed that at the interface of alumina and the NiTi matrix, Ti-rich phases had evolved, while in the grain interiors, matrix decomposition mostly led to the formation of Ni-rich intermetallics. High-resolution transmission electron microscopy investigations confirmed an increased Ni/Ti ratio in the austenitic NiTi matrix in the vicinity of the Ti-rich phases, and the formation of martensitic NiTi near the Ni-rich phases. The results from differential scanning calorimetry indicated that the latent heat of martensitic transformation in the SPS composite is higher than that of HIP-processed composite samples due to lower matrix decomposition and higher NiTi phase, which can participate in martensitic transformation.</P>

초음파 분무 열분해와 가압소결로 제조한 이트리아 분산입자 강화 텅스텐의 특성

이의선,허연지,김지영,이영인,석명진,오승탁 대한금속·재료학회 2023 대한금속·재료학회지 Vol.61 No.3

The effects of fabrication method on the microstructure and sinterability of W-1 wt% Y2O3 wereanalyzed. W composite powders dispersed with Y2O3 particles were synthesized by the ultrasonic spraypyrolysis process or the ultrasonic spray pyrolysis/polymer solution process. A dense composite was fabricatedby a combination of spark plasma sintering and final hot isostatic pressing. The powder synthesized by theultrasonic spray pyrolysis had fine dispersed particles on the surface of the cubic powder and was composedof W, Y2O3 and W-oxides. On the other hand, in the case of the ultrasonic spray pyrolysis/polymer solutionprocess, the nano-sized particles formed agglomerates and existed only as pure W and Y2O3 phases. All thesintered compacts treated with HIP showed an increase in relative density, and the sintered compacts of thepowder synthesized by the ultrasonic spray pyrolysis/polymer solution process showed a maximum relativedensity of 97~99% and a fine grain size. The change in microstructure with different powder processing wasexplained by the presence of W-oxide and the size and distribution of Y2O3 particles. The Vickers hardnessof the sintered compact reached the largest value of about 5 GPa in the powder synthesized by the ultrasonicspray pyrolysis/polymer solution process, which was interpreted to be a result of the relatively high densityand decreased grain size.

Ti-Si 및 Ti-Fe-Si 주조합금의 열간정수압 성형에 의한 티타늄 실리사이드의 형성과 결정학적 특성

鄭喜元,金承彦,玄容宅,李龍泰 대한금속재료학회 2001 대한금속·재료학회지 Vol.39 No.12

The silicon addition in the titanium alloys yields the solid solution and titanium silicides. The morphology and distribution of the titanium silicides depend upon the alloy chemistry or the heat treatment condition, and play an important role in improving the mechanical properties of the alloys. In this study, the morphology, formation process, and crystallographic characteristics of the titanium silicides in the Ti-Fe-Si alloy system were studied. Three types of silicides were found in the alloys; (1) interconnected chain-like silicides at grain boundary, (2) coarse silicides over 1 ㎛, (3) fine silicides less than 0.2 ㎛. Ti_3Si was dominant in cast + HIP condition while Ti_5Si_3 was dominant in as-cast state. It is recognized that Ti_5Si_3 → Ti_3Si transition occurred by the peritectoid reaction and it may be promoted by pressure during HIP. However, in the case of the fine silicides, Ti_3Si and Ti_5Si_3 were found simultaneously even after HIP. Such a fine silicide was found to have crystallographic orientation relationship with β matrix.

Experimental and Simulaton Anaylysis of Hot Isostatic Pressing of Gas Atomized Stainless Steel 316L Powe Compacts

( Dongguo Lin ),( Sangyul Ha ),( Youngho Shin ),( Dong Yong Park ),( Seong Jin Park ),( Sung Taek Chung ),( Ravi Bollina ),( Seongkyu See ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.10

In this work, both experimental and numerical studies were conducted to investigate the densification behavior of stainless steel 316L (STS 316L) powders during hot isostatic pressing (HIP), and to characterize the mechanical properties of HIPed specimens. The HIP experiments were conducted with gas atomized STS 316L powders with spherical particle shaped under controlled pressure and temperature conditions. The mechanical properties of HIPed samples were determined on a series of tensile tests, and the results were compared to a reference STS 316L sample prepared by the conventional process, i.e., extrusion and annealing process. Corresponding microstructures before and after tensile tests were observed using scanning electron microscopy and their relationships to the mechanical properties were addressed. Furthermore, a finite element simulation based on the power-law creep model was carried out to predict the density distribution and overall shape change of the STS316L power compact during HIP process, which agreed well with the experimental results.

Fabrication and mechanical properties of powder metallurgy tantalum prepared by hot isostatic pressing

Kim, Y.,Kim, E.P.,Noh, J.W.,Lee, S.H.,Kwon, Y.S.,Oh, I.S. MPR Pub. Services 2015 INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HAR Vol.48 No.-

The fabrication process of a powder metallurgy (P/M) tantalum product with full density and fine microstructure was developed by using cold and hot isostatic pressing techniques. In order to increase the compact density and make the uniform density distribution, cold isostatic pressing (CIPing) of tantalum powders was conducted. Prior to hot isostatic pressing (HIPing), the CIPed billet was encapsulated and degassed to remove the contaminants in the container. After degassing, HIPing was performed twice and full densification of the tantalum powders was accomplished, regardless of powder size. The effect of processing conditions on the microstructure and mechanical properties of P/M tantalum billets was investigated. As the number of processing steps and temperature increased, the grain size of HIPed tantalum billets increased. Moreover, contrary to the Hall-Petch relation, the mechanical strength was increased in spite of increasing the grain size. This is because the oxygen content of the billets increased with rising in temperature and the number of processing steps. Therefore, in case of tantalum, it is found that the mechanical properties of tantalum may be highly influenced by the amount of interstitial elements, especially oxygen, rather than microstructural properties.

열처리 및 HIP 공정을 이용한 가스터빈 고온부품 재생시 미세조직 및 기계적 특성 변화

장성용,오기용 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.7

The evolution of microstructure and mechanical characteristics during the rejuvenation of a hot gas pass component of a gas turbine was investigated with an actual service-exposed bucket in a power plant. Heat treatment and hot isostatic pressing processes were conducted to rejuvenate a hot gas pass component of a F class gas turbine which had been operated for 101.15% of its expected lifetime. In the three step heat treatment, the specimens were exposed to 1210 oC, 1120 oC, and 845 oC for periods of 2 h, 2 h, and 24 h, respectively, with rapid cooling. Then, the specimens were exposed to conditions of 1200 oC and 100 MPa for 4 h to enhance their integrity. Analysis of the microstructure determined that after heat treatment the average size of γ' decreased around 60 μm, while the area fraction of γ' increased around 20% compared to before heat treatment. With respect to mechanical characteristics, the samples’ stress-rupture time, yield strength, and ultimate strength improved with heat treatment and hot isostatic pressing, while hardness did not show any meaningful variation. These phenomenological results suggest that heat treatment and hot isostatic pressing play a critical role in the rejuvenation of a hot gas pass component, and can provide an operating and maintenance strategy to enhance the economic feasibility of a combined cycle power plant.

Modeling of materials behavior at various temperatures of hot isostatically pressed superalloys

Lee, K.O.,Lee, S.B. Elsevier Sequoia 2012 Materials science & engineering. properties, micro Vol.541 No.-

It is very important to be able to predict material behaviors at low and high temperatures for the design and manufacturing of reliable elevated-temperature systems. Superalloys are widely used on most liquid rocket engines for space launch vehicles or gas turbine engines where they experience hot temperature gases and low temperature fluids like liquid oxygen. Hot isostatic pressing (HIP) is one of the manufacturing methods for developing these materials. In this research, three superalloys, HIP Inconel 718, HIP Rene 95, and HIP Astroloy, were investigated at elevated temperatures. Serrated flow induced by dynamic strain aging (DSA) was observed in certain temperature regions where the embrittlement of the materials progressed. A dislocation barrier model was modified to describe the material behavior including dynamic strain aging and creep relaxation effects observed at high temperatures. The suggested model was found to predict well the deformation behaviors of the superalloys from low temperatures to elevated temperatures.

Vitrification Analysis of Washing Sludges From Stainless Steel Tank Using Hot Isostatic Press & High-Temperature Furnace

Jaeho Lee,Hee Reyoung Kim,Ki Joon Kang,Sia Hwang 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

The optimum vitrification conditions of the radioactive waste using high-temperature furnace and HIP (Hot Isostatic Press) were studied for the successful reduction of the solidification volume, radioactive level, satisfying the disposal criteria such as leaching rate and compressive strength. Vitrification is receiving attention for the solidification disposal of intermediate and low-level radioactive wastes for its chemical-physical stability and leachability. Its principle is to trap the radioactive material in a fixed structure of the glass type materials, such as Boron Trioxide, Silicon Dioxide and Phosphorus Pentoxide. Sludge targeted in this study is assembly of materials while sludge is stored in the stainless-steel tank before disposal, which consists of Fe3O4 (14.9wt%), Fe2O3 (3.8wt%), and Cr2O3 (6.3wt%), cement paste (25wt%) and detergent/shower sludge (50wt%). The detergent/shower sludge generated from the washing the clothes that were worn during the work at the laboratory and nuclear power plant contains organic materials that are vulnerable to chemical reactions, therefore, immobilization of organic material by the incinerating step, which can also immobilize the radioactive substance, was applied. Its composition – containing Cs-133 and Co-59 substitution for Cs-134 and Co-60 that are radioactive – was analyzed by XRD before and after the mineralization of the sludge using high temperature furnace in different temperature, to identify the remaining element and the features of the mineralized sludge. Targeted sludge was vitrificated using Hot Isostatic Press in with different pressure and temperature conditions, to find out the optimum vitrification conditions. Vitrificated waste was evaluated in many aspects - leaching evaluation following ANS16.1, compressive strength evaluation of 3.44 MPa (waste disposal criteria), volume reduction before and after the sequence.

Historical Review and Future of Hot Isostatic Pressing Equipment

Cliff Orcutt,성형동(H. D. Sung),김승수(S. S. Kim),최미영(M. Y. Choi),이재우(J. W. Lee) 한국정밀공학회 2011 한국정밀공학회 학술발표대회 논문집 Vol.2011 No.6월

Hot Isostatic Pressing 기술 적용 원전 해체폐기물 처리 국내 활용 방안 연구

박기현,이경호,정세원,김태만 (사)한국방사선산업학회 2022 방사선산업학회지 Vol.16 No.1

The R&D of technologies for treating efficiently various and large quantity of decommissioningwastes, which are produced during decommissioning of nuclear power plants, are proceedingactively over the world. Especially the technologies for reduction of waste volume are welcomedand these are super compaction, melting, thermochemical treatment, etc. to meet the type andcharacteristics of wastes. The combined technology of sintering and compaction technology, namely HotIsostatic Pressing (HIP) is the technology developed in 1953 firstly by ASEA for diamond processing [1]and is the technology to press the target isostaticly by using inert gas at about 1,000°C and 100~200MPa (about 1,000~2,000 atm), and is well welcomed recently in Japan and England, etc. in the field ofradioactive waste treatment because of high compaction capability. Thus this paper investigates thevarious cases using HIP technology and suggests the application possibility for the reduction of volume oflocal decommissioning wastes.