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Indegeneous development of a ultra high strength steel with stainless property for space application

Primary Information

Domain

Advanced Materials

Project No.

6456

Sanction and Project Initiation

Sanction No: F. No.: 3-18/2015-TS-TS.I

Sanction Date: 29/11/2016

Project Initiation date:08/02/2017

Project Duration: 36

Partner Ministry/Agency/Industry

Ministry of Human Resource Development Ministry of Steel Department of Space

Role of partner:MHRD and MoS are co-funding the material development project. Department of Space (ISRO) is one of the end users of this material. Mr. Tharian and Mr. ANoop of LPSC ISRO are actively involved in this material developmental program. Material is being developed in MIDHANI.

Support from partner:MHRD and MoS are co-funding the material development project. MHRD: 140.5 lakhs INR MoS: 140.5 lakhs INR Dept. of Space: ISRO is one of the end users of the material being developed. LPSC, ISRO is actively involved in the material development program MIDHANI: MIDHANI is involved in the production and evaluation of mechanical properties

Principal Investigator

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Sujoy Kumar KarPrimary
Indian Institute of Technology Kharagpur

Host Institute

Co-PIs

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Shiv Brat Singh
Indian Institute of Technology Kharagpur

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K Thomas Tharian
Liquid Propulsion Systems Center, ISRO, Thiruvananthapuram

Scope and Objectives

The goal of the project was to indigenize the material development for a high strength, high fracture toughness, and corrosion resistant steel (as per AMS 5936 specification) for space and aerospace applications.

Deliverables

1. After material development in industrial scale (2.5 ton heat) and realization of various products at M/s. MIDHANI, material required for characterizations and metallurgical study shall be delivered to IIT Kharagpur and balance material as given below will be delivered to LPSC, ISRO.
2. Forging to different diameters to realize rods of diameters 100 mm, 150 mm and 200 mm in solution annealed and proof machined condition.
3. Forging to thick slabs and conversion to sheets/plates up to 5 mm thickness x 1000 mm L in solution annealed and passivated condition
4. Strips of sizes 1.5(+0.1/+0.2) x 30(+0.2) x 1600 mm length (or multiples) and 2.6(+0.1/+0.2) x 30(+0.2 )x 6000 mm length (or multiples) in solution annealed condition, descaled with bright finish.
5. Filler wire 1.2/1.6 mm dia for welding studies.

Scientific Output

Various trial heats of size 2.5-ton primary melt were made using vacuum induction melting ((VIM), which is the primary melt) and vacuum arc remelting ((VAR), which is the melting step) and subsequent homogenization, forging, solutionizing, cryo treatment and aging treatments were given. Properties have been evaluated. Characterizations of microstructure, microtexture, and compositions have been carried out. Strength properties and longitudinal ductility have been achieved above specification (UTS more than 1700 MPa and %reduction in the area more than 35% in the longitudinal direction) for all the trial heats so far. Following conclusions are drawn from the study carried out on initial heats of indigenous material produced by MIDHANI Initial heats of the indigenous material showed promising results for the strength properties. However indigenous material showed poorer transverse ductility as compared to the imported material. Comparative characterization (using optical and electron (SEM, TEM, EBSD, EDS) microscopy) work carried out on the indigenous as well as imported samples has revealed the following: 1. Inclusions (TiN and MnS) are more in indigenous samples. Imported steel is much cleaner. 2. Banding was observed in the microstructure of indigenous samples, which is absent in the imported sample. 3. The higher quantity of retained austenite present in the microstructure of indigenous material, whereas it is minimal in the imported sample. 4. From ODF analyses, it is observed that the imported sample shows a distinct Goss and rotated Goss texture, whereas the indigenous sample shows scattered texture. 5.TEM study revealed the morphology of martensitic microstructure (lath structure, lath boundaries, block boundaries, packet boundaries) in imported and indigenous samples. 6. Ni3Ti precipitates have been observed. 7. Various phase transformation temperatures (precipitation (Ni3Ti) start and finish, austenite start and finish and martensite start) have been measured from dilatometry study. The results are listed in a table in the enclosed figure. Thermodynamic calculations were also carried out to study the phase stability. It shows the fraction of various equilibrium phases as a function of temperature. Following phases are found to exist in equilibrium: Ferrite (martensite), Ni3Ti, (Cr, Mo)23C6, TiC, Cr rich BCC phase, Laves_C14 phase (intermetallic phase of Fe, Mo, Ni, and Cr), retained austenite.

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Results and outcome till date

Industrial scale trial heats have been made at MIDHANI. All the properties met the specifications except the transverse ductility for some of the trial heats. Extensive characterization work has been carried out using SEM, EDS, EBSD, TEM, OM along with quantified analyses of microstructure and composition. It is found that indigeneous material has
1. Banding microstructure (observed in optical microstructure). EDS study shows that this may be due to strain inhomogeneity.
2. More. retained austenite compared to the imported material
3. higher amounts of inclusions (TiN and MnS) as compared to the imported material
4. Nano scale Ni3Ti precipitates have been found to be the main strengthening phase
5. EBSD analysis shows that the indigenous sample has more random texture. Whereas the imported sample shows Goss and rotated Goss texture.

Societal benefit and impact anticipated

The material being developed indigenously has wide range of applications, especially in space and aerospace, because of its optimum combination of strength, fracture toughness and corrosion resistance. Indigenous development of this material will reduce the cost by not having to import. It will benefit the country's economy. Once the indigenous material gets through with all requirements, then there will be a constant demand from Space, Nuclear and defense sectors.

Next steps

Issues of microstructure like banding and retained austenite are to be fixed. For removing the banding structure upset forging, variation in forging parameters and variation in solutionizing time have been planned. For retained austenite, cryo treatment is to be checked. Hence, following actions will be taken next.
1) On a fresh heat MIDHANI will carry out homogenization treatment at 1250 degree centigrade for 20 hours and impart upset forging from 950 mm to 500 mm followed by draw down operations.
2) On the samples from forged bars that showed poor transverse ductility, effect of variation in solutionizing temperature (980 +/- 14 deg C) and time on banding microstructure will be checked. If the banding is due to strain inhomogeneity banding may go away by proper solutionizing treatment.
3) Microstructure study will be carried out at various steps of processing (for as cast, as forged, as solution treated, as cryo treated and after aging).
4) Retained and reverted austenite are to be quantified by XRD and as well as EBSD before and after aging treatment.
5) Texture analysis of forged samples from the center to the periphery will be carried out.
6) Ms and Mf temperatures will be identified through cryo DSC.
7) ISRO will look into the effect of changing various forging parameters in their 1000 ton press facility at VSSC.

Publications and reports

Paper in review stage for publication in the special issue of the IIM Transactions in January 2019. It has been presented in the International Conference of Advanced Materials and Manufacturing Processes for Strategic Sectors (ICAMPS 2018) held in Trivandrum during 25-27 October 2018.

Patents

NA

Scholars and Project Staff

Research Scholar (1): Mr. Govardhana Poojari, Research Scholar, 2017 - Present Dual degree student (1): Mr. Amit Kumar Ram, Dual degree final year, 2017- present

Challenges faced

The microstructure and related properties of the material developed in industrial scale depend on the melting and processing capabilities of the country's only such infrastructure (VIM and VAR) available at MIDHANI, Hyderabad.

Other information

Work is as per schedule. The team is confident of the present material development program for space application.

Financial Information

  • Total sanction: Rs. 281 lakhs

  • Amount received: Rs. 281 lakhs

  • Amount utilised for Equipment: Rs. 57.15 lakhs

  • Amount utilised for Manpower: Rs. 0.85 lakhs

  • Amount utilised for Consumables: Rs. 1.42 lakhs

  • Amount utilised for Contingency: Rs. 0.77 lakhs

  • Amount utilised for Travel: Rs. 1.2 lakhs

  • Amount utilised for Other Expenses: 80.44 lakhs

  • Amount utilised for Overheads: Rs. 49.17 lakhs

Equipment and facilities

Software/ Equipment: Software: 1)ThermoCalc and DICTRA with databases TCFE7 and MOBFE2 respectively Equipments: 2) Optical Microscope 3) Dual disc polishing machine 4) Microprocessor controlled electropolisher 5) Precision cutting low speed diamond cutter (yet to be received) 6) Computer workstation with printer (yet to be purchased) Facilities created: --- Lab tables + desks + cabinets --- Fume hood for the electro polisher