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Hyderabad, India

Anil Kumar V.,Vikram Sarabhai Space Center | Anil Kumar V.,Indian Institute of Technology Bombay | Murty S.V.S.N.,Vikram Sarabhai Space Center | Gupta R.K.,Vikram Sarabhai Space Center | And 2 more authors.
Transactions of the Indian Institute of Metals | Year: 2015

β-Titanium alloys form one of the most versatile classes of structural materials due to their high specific strength, good hardenability, crack propagation resistance and substantial ductility. β-Titanium alloy with a composition (in wt%) of Ti–5Al–5Mo–5V–1Cr–1Fe was processed by double vacuum arc remelting route. In the present work, the effect of boron addition (up to 0.12 wt%) on the as-cast microstructure and β-transus (Tβ) of the alloy was studied using characterization tools like optical microscopy, electron back scattered diffraction, scanning electron microscopy, differential scanning calorimetry (DSC) and dilatometry. It was observed that boron addition has resulted in refinement of the as-cast microstructure due to precipitation of titanium boride whiskers along the grain boundaries. The DSC and dilatometry studies on the as-cast alloy revealed significant effect of boron addition on thermal stability of the alloy. © 2015, The Indian Institute of Metals - IIM.

Narayana Rao M.,Mishra Dhatu Nigam Ltd
Energy Procedia | Year: 2011

Materials play very crucial role for a safe, reliable and economic operation of nuclear power plants. Materials used in nuclear reactors encounter hostile environment and aggressive media during service, and are expected to retain their structural and metallurgical integrity over a long period of use. The major challenges are the effect of radiation on embrittlement, creep, erosion, corrosion, radiation induced growth, swelling, stress corrosion cracking, hydrogen embrittlement and radioactivity build up. In order to realize a high degree of reliabilit y and at the same time meet the imposing challenges, material specification and acceptance criteria are extremely stringent and the products have to undergo a detailed testing and characterization prior to their use. To ensure the conformance to the specification, processes need to be developed which involves melting the alloy with stringent chemistry control, optimizing thermo-mechanical treatment and modifying heat treatment schedule suitably to achieve mechanical properties. A typical nuclear power plant makes use of nuclear fuel materials such as uranium, structural materials such as zirconium alloys, stainless steels, nickel base alloys as well as low alloy and carbon steels. The paper outlines processing methodologies and gives an overview of some of the structural materials. © 2011 Published by Elsevie Ltd.

Narayana Rao M.,Mishra Dhatu Nigam Ltd
Transactions of the Indian Institute of Metals | Year: 2010

MIDHANI has been producing special stainless steels for different sectors. Production of these steels has posed challenges with respect to control over chemical composition, designing heat treatment parameters to meet the desired properties. The most challenging grades have been SS304L, 13-8 PH and 9Cr1Mo steels to name a few. The melting equipments were selected with utmost care and processing was done to meet the specified properties. In case of 304L grade in order to meet corrosion resistance requirements, elements like Silicon, Carbon and Sulphur were required to be controlled in very low limits. Production of 13-8 PH steels demanded that a combination of high strength and toughness are achieved. © 2010 TIIM, India.

Narahari Prasad S.,Mishra Dhatu Nigam Ltd | Narayana Rao M.,Mishra Dhatu Nigam Ltd
Advanced Materials Research | Year: 2013

Stainless Steel is a family of versatile materials that has been put into a wide variety of application by mankind. Stainless steels are iron-based alloys containing minimum 12% chromium and upto 25% nickel with minor additions of carbon, nitrogen, molybdenum, tungsten, titanium, niobium, copper and selenium. It has a wide range of applications from small pins to the construction of automobiles, petrochemical, space, aeronautical, ship building industries, nuclear and thermal power stations. Certain grades of stainless steels, because of their biocompatibility are used for manufacture of biomedical implants. In fact steel touches every sphere of our daily life. By and large stainless steel family consists of hundreds of grades with varieties of compositions and a large spectrum of mechanical properties. The corrosion and oxidation resistance of stainless steels have been significantly improved through fine-tuned chemical compositions and microstructural constituents, leading to the evolution of super stainless steels. Stainless steel development from design to application is a long-term continuous effort. The recent advances in stainless steels are mainly due to new ways of manufacture, processing and usage of advanced equipments. In spite of inroads by a range of competing materials, stainless steels occupy an important place as structural materials, because of their outstanding strength to weight ratios, ductility, fracture toughness, repairability, corrosion, etc for a given cost. Over the years, MIDHANI has catered to the requirements of Indian Space, Nuclear, Thermal, aeronautical and Defence sector for many high performance materials. A wide range of special stainless steels - many of them being tailor made to customer's specific needs have been developed and supplied. This has been possible with the help of state of the art facility and excellent quality assurance system available in MIDHANI. The presentation will high light MIDHANI role in development and commercial production of different varieties of stainless steels for critical applications. © (2013) Trans Tech Publications, Switzerland.

Jayakumar T.,Indira Gandhi Center for Atomic Research | Mathew M.D.,Indira Gandhi Center for Atomic Research | Laha K.,Indira Gandhi Center for Atomic Research | Albert S.K.,Indira Gandhi Center for Atomic Research | And 6 more authors.
Fusion Science and Technology | Year: 2014

India is one of the countries associated with the development and testing of test blanket modules (TBMs) in ITER. Accordingly, India has taken up development of 9Cr-W-Ta reduced activation ferritic martensitic (RAFM) steel, which is the structural material chosen for TBMs, together with the associated manufacturing technologies required for TBM fabrication. With the objective of developing an India-specific RAFM steel, four heats of RAFM steel with tungsten and tantalum contents varying in the ranges 1 to 2 wt% and 0.06 to 0.014 wt%, respectively, were melted. The steel was melted through vacuum induction melting and vacuum arc refining routes with strict control over the amounts of elements that induce radioactivity (Mo, Nb, B, Cu, Ni, Al, Co, and Ti) and the elements that promote embrittlement (S, P, As, Sb, Sn, Zr, and 0). Extensive characterization of the microstructure and mechanical properties of the steel was carried out. The ductile-to-brittle transition temperature of the steel increased slightly with increasing tungsten and tantalum content. The tensile strength of the steel was found not to change significantly with increasing tungsten content; however, it decreased marginally with increasing tantalum content, with a consequent increase in ductility. The creep rupture strength of the steel at 823 K was found to increase significantly with increasing tungsten content, whereas it decreased with increasing tantalum content. The low-cycle fatigue life of the steel at 823 K was found to increase with increasing tungsten and tantalum content; however, extensive cyclic softening was exhibited when the tungsten content was >1.4 wt%. RAFM steel containing 1.4 wt% tungsten and 0.06 wt% tantalum was found to have a better combination of strength and toughness and is specified as Indian RAFM (INRAFM) steel. The joining technologies adopted for the fabrication of a TBM are hot isostatic pressing to produce the first wall, followed by gas tungsten arc (GTA), electron beam (EB), laser, and laser hybrid welding for joining the rest of the TBM. Welding techniques for joining RAFM steel have been developed and characterized. The properties of the GTA welds met the full specifications of the requirement and were comparable to the properties of the base metal. This consumable has also been used to carry out hybrid laser welding successfully. A procedure for using EB welding to join plates of thicknesses up to 12 mm has been developed. Impact tests conducted on EB welds showed that the toughness of the weld metal in the as-welded condition is comparable to that of the base metal. A box structure that simulates one of the components of a TBM has been fabricated using EB welding to demonstrate the applicability of the process to component fabrication. Laser welding of 6-mm-thick plates of RAFM steel has also been carried out successfully, and the properties of the weld joints have been found to be satisfactory. This paper discusses the development of INRAFM steel and its properties and the current status of the fabrication technologies being developed for fabrication of the Indian TBM to be tested in ITER.

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