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Development and application of small scale bending tests for residual property assessment of high temperature materials in turbines

Primary Information

Domain

Advanced Materials

Project No.

4035

Sanction and Project Initiation

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

Sanction Date: 29/11/2016

Project Initiation date: 1/3/2017

Project Duration: 36

Partner Ministry/Agency/Industry

Ministry of Power

 

Role of partner: BHEL R & D, Hyderabad is our partner in this study. They have supplied materials (boiler tubes, e.g., T11 and T22 in different usage conditions, turbine shaft, IN 718) relevant to power industry for testing. Our partner has also shared relevant data available with it.

 

Support from partner: Partner has made material available for testing and shared data available with it.

Principal Investigator

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Professor Vikram Jayaram
Indian Institute of Science

Host Institute

Co-PIs

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Dr. Praveen Kumar
Indian Institute of Science

 

Scope and Objectives

Overall objective: Development and demonstration of utility of creep in bending for residual life assessment of high temperature materials used in power plants Sub-objectives: o Development of methodology of performing creep tests in bending: Completed o Performing experiments on materials provided by industry partner: Materials (boiler tubes, steel and CCA 617 superalloy) have been obtained from BHEL, tests are being performed o Employment of sample with small volumes: Partially completed; Further optimization is being performed o Intelligent prediction of residual creep properties of in-service components in power plants: On-going o Examination of length-scale dependence of properties: On-going

Deliverables

a. A test methodology that will allow creep to be evaluated on beams of cross section extending from a few mm. downwards. This methodology will include details of specimen preparation, finite element and analytical modelling to relate applied loads and measured cantilever displacements and surface strain distribution to classical creep parameters.
b. Validation of bending creep parameters, such as stress exponent, minimum creep rate and activation energy, against uniaxial data. These will be generated on industry-supplied Cr-Mo steels and Ni-based alloys, both in the as-fabricated condition as well as after service / service-simulated exposure. Microstructural characterization of samples tested under different conditions will be performed.
c. Correlation of microstructural changes with changes in creep behavior. A comparison with ASTM standard samples with that of the miniaturized test samples will be made. d. Recommendations on the applicability of this technique for residual life prediction of in-service components.

Scientific Output

A scientific outcome will be the understanding of how sample size may affect measured creep properties in the range of 0.1 -1.0 mm.

Results and outcome till date

1. Numerical technique can be used to predict the stress profile and strain variation across thickness of a cantilever deforming according to power-law creep.
2. Numerical technique can be used to accurately predict the creep curve in bending, including primary and secondary stages.
3. Steady state creep is attained under creep in bending. Plotting the steady state strain rate as function of stress, as obtained from bending creep experiments, can be used to determine important creep parameters, such as stress exponent.
4. Preliminary creep tests on boiler tube samples show that bending creep is sensitive to the service condition of the material (for example, it reveals noticeable difference in the steady state creep rates for virgin tubes and in-service tubes). Based on results obtained so far in this study, we can conclude the following regarding novelty and technological promise of creep in bending: a. Creep in bending can be used to accurately predict the creep behavior in steady state of a material. Since performing a test in bending precludes usage of complex grips and alleviates alignment problem, this technique is particularly useful for testing difficult to machine as well as small sized samples. b. Creep in bending, in principle, is a small volume testing technique, wherein the creep behavior of entire cantilever is dominated by the response of material at the fixed end. This, thereby, allows testing materials whose volume is limited by using the idea of composites. This has tremendous technological importance, especially for testing materials scooped from components without affecting its regular operation.

 

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Societal benefit and impact anticipated

This project has an indirect societal impact: It can potentially minimize the down time for a power plant, which is often needed for inspection and lifing purposes.

Next steps

We will continue studying creep behavior of T11, T22 and IN 718 alloys under bending. The new works will be more focused on quantifying the remaining life of a material which has been service for several years. Also, we will try to disseminate the obtained knowledge to BHEL and other interested industries.

Publications and reports

None

Patents

None

Scholars and Project Staff

Jyotirmaya Kar (Post-doctoral fellow, July 2017- till date)
Syed Ali (PhD student, March 2017- till date)
Priya Goel (PhD student, March 2017- till date)
Faizan Hizazi (ME student, March 2017 - July 2018 and now as PhD student, August 2018- till date)
Shreehard Sahoo (ME student, August 2017 - till date)
Devi Lal (Project assistant, November 2018 - till date)
Kaustubh Venkatraman (Project assistant, July 2018-November 2018)
Bharathi N. (continuing as Administration coordinator)
Kantharaj N A (continuing as technical operator)
Sasishara (Continuing as technical operator)


Challenges faced

None

Other information

None

Financial Information

  • Total sanction: Rs. 2,30,02,000

  • Amount received: Rs. 1,34,76,000

  • Amount utilised for Equipment: Rs. 5,79,970

  • Amount utilised for Manpower: Rs. 24,06,852

  • Amount utilised for Consumables: Rs. 14,25,174

  • Amount utilised for Contingency: Rs. 12,43,506

  • Amount utilised for Travel: Rs. 1,46,908

  • Amount utilised for Other Expenses: NIL

  • Amount utilised for Overheads: Rs. 22,46,000

Equipment and facilities

 

Dead-weight creep machine including furnace has been installed. A motorized mini-mechanical tester is being ordered.