CHARACTERIZATION OF MARTENSITIC STAINLESS STEELS WITH HIGH SILICON CONTENT by Sreenivas Kohir Bachelor of Engineering in Mechanical Engineering Chaitanya Bharathi Institute of Technology, Osmania University, India May 2005 A thesis submitted in partial fulfillment of the requirements for the Master of Science Degree in Mechanical Engineering Department of Mechanical Engineering Howard R. Hughes College of Engineering Graduate College University of Nevada, Las Vegas December 2007
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CHARACTERIZATION OF MARTENSITIC STAINLESS STEELS
WITH HIGH SILICON CONTENT
by
Sreenivas Kohir
Bachelor of Engineering in Mechanical Engineering Chaitanya Bharathi Institute of Technology, Osmania University, India
May 2005
A thesis submitted in partial fulfillment
of the requirements for the
Master of Science Degree in Mechanical Engineering Department of Mechanical Engineering
Howard R. Hughes College of Engineering
Graduate College University of Nevada, Las Vegas
December 2007
ii
Thesis Approval Page
Provided by Graduate College
iii
ABSTRACT
Characterization of Martensitic Stainless Steels with High Silicon Content by
Sreenivas Kohir
Dr. Ajit K. Roy, Examination Committee Chair Professor of Mechanical Engineering,
University of Nevada, Las Vegas
The tensile properties and corrosion resistance of martensitic 12Cr-1Mo steel
containing 3 and 4 weight percent (wt%) Silicon (Si) have been evaluated in this
investigation. The tensile data indicate that limited plasticity in terms of failure strain (ef)
was observed at room temperature irrespective of the Si content. A significant drop in ef
was observed with the steel containing 3 wt% Si at 400oC. For both alloys, there was a
gradual drop in tensile strength with increasing temperature. The steel containing 3 wt%
Si exhibited the maximum cracking susceptibility in the 90oC acidic solution, when tested
by the slow-strain-rate technique. This alloy also showed enhanced cracking tendency in
the same environment under controlled cathodic potential (Econt). However, the steel
containing 4 wt% Si did not exhibit any effect of temperature and Econt on its cracking
tendency. The magnitude of corrosion potential became more active (negative) with
increasing temperature. The final stress intensity factor was significantly reduced at
higher applied loads imparted by wedges in 100oC acidic solution. In general, the tested
specimens exhibited brittle failures, as characterized by scanning electron microscopy.
iv
TABLE OF CONTENTS
ABSTRACT....................................................................................................................... iii LIST OF TABLES............................................................................................................. vi LIST OF FIGURES .......................................................................................................... vii ACKNOWLEDGEMENTS............................................................................................... ix CHAPTER 1 INTRODUCTION ........................................................................................ 1 CHAPTER 2 TEST MATERIALS SPECIMENS AND ENVIRONMENTS.................... 6 2.1 Material .................................................................................................................. 6 2.2 Test Specimens ...................................................................................................... 8 2.2.1 Smooth Cylindrical Specimen ...................................................................... 8 2.2.2 Polarization Specimen .................................................................................. 9 2.2.3 Double-Cantilever-Beam Specimen ........................................................... 12 2.2.4 Cylindrical Specimen for Controlled Potential Testing.............................. 14 2.3 Test Environments ............................................................................................... 14 CHAPTER 3 EXPERIMENTAL PROCEDURES........................................................... 16 3.1 Tensile Properties Evaluation .............................................................................. 16 3.2 Cyclic Potentiodynamic Polarization Testing...................................................... 19 3.3 Stress Corrosion Cracking Testing ...................................................................... 24 3.3.1 Slow-Strain-Rate Testing............................................................................ 24 3.3.2 Slow-Strain-Rate Testing............................................................................ 27 3.3.3 Slow-Strain-Rate Testing............................................................................ 30 3.4 Microstructural Evaluation .................................................................................. 31 3.5 Fractographic Evaluation ..................................................................................... 32 CHAPTER 4 RESULTS................................................................................................... 34 4.1 Metallographic Microstructure ............................................................................ 34 4.2 Tensile Properties Evaluation ............................................................................. 36 4.3 Results of SCC Testing........................................................................................ 42 4.4 Results of CCP Testing........................................................................................ 44 4.5 SCC Testing under Controlled Potentials ............................................................ 49 4.6 Results of DCB Testing ....................................................................................... 51 4.7 Fractographic Evaluation ..................................................................................... 55
v
CHAPTER 5 DISCUSSION............................................................................................. 65 CHAPTER 6 SUMMARY AND CONCLUSIONS......................................................... 68 APPENDIX A INSTRON TEST DATA.......................................................................... 70 APPENDIX B SSR TEST DATA .................................................................................... 75 APPENDIX C CPP TEST DATA .................................................................................... 78 APPENDIX D SCC TEST DATA UNDER Econt............................................................. 81 APPENDIX E UNCERTAINTY ANALYSES OF EXPERIMENTAL RESULTS........ 83 BIBLIOGRAPHY............................................................................................................. 92 VITA................................................................................................................................. 94
vi
LIST OF TABLES
Table 2.1 Typical Tensile Properties of 12Cr-1Mo Steel ................................................. 7 Table 2.2 Physical Properties of 12Cr-1Mo Steel ............................................................ 7 Table 2.3 Chemical Compositions of Cr-Mo Steels Tested ............................................. 8 Table 2.4 Thickness of Wedges used.............................................................................. 13 Table 2.5 Chemical Composition of Test Solution (gm/liter) ........................................ 15 Table 3.1 Specifications of the Model 8862 Instron Equipment .................................... 19 Table 3.2 Specifications of Electron Beam and Dose Rate ............................................ 23 Table 4.1 Tensile Strength vs. Temperature ................................................................... 39 Table 4.2 Ductility vs. Temperature ............................................................................... 39 Table 4.3 Results of SSR Testing ................................................................................... 44 Table 4.4 Results of CPP Testing ................................................................................... 48 Table 4.5 Results of SSR Testing under Controlled Potentials ...................................... 51 Table 4.6 Results of DCB Testing .................................................................................. 53
vii
LIST OF FIGURES
Figure 1.1 Production of Fission Products and Minor Actinides.................................... 2 Figure 2.1 Configuration of Smooth Cylindrical Specimen ........................................... 9 Figure 2.2 Configuration of the Polarization Specimen ............................................... 10 Figure 2.3(a) Dimensions of DCB Specimen ................................................................... 11 Figure 2.3(b) Pictorial view .............................................................................................. 12 Figure 2.4 Double-TaperWedge ................................................................................... 13 Figure 2.5 Spot-Welded Specimen for Econt Testing .................................................... 14 Figure 3.1 Tensile Testing Setup .................................................................................. 17 Figure 3.2 Cyclic Potentiodynamic Polarization Curve ............................................... 21 Figure 3.3 CPP Test Setup ............................................................................................ 22 Figure 3.4 Luggin Probe Arrangement ......................................................................... 22 Figure 3.5 Standard Potentiodynamic Polarization Plot (ASTM G 5) ......................... 23 Figure 3.6 CERT Machines for SSR Testing................................................................ 26 Figure 3.7 Autoclave Test Setup................................................................................... 28 Figure 3.8 SCC Test Setup under Econt ......................................................................... 31 Figure 3.9 Leica Optical Microscope............................................................................ 32 Figure 3.10 Scanning Electron Microscope.................................................................... 33 Figure 4.1 Optical Micrograph of Steel with 3 wt% Si, 5% Nital, 500X ..................... 35 Figure 4.2 Optical Micrograph of Steel with 4 wt% Si, 5% Nital, 500X ..................... 36 Figure 4.3 s-e Diagrams of Steel Containing 3 wt% Si vs. Temperature ..................... 37 Figure 4.4 s-e Diagrams of Steel Containing 4 wt% Si vs. Temperature ..................... 37 Figure 4.5 YS vs. Temperature ..................................................................................... 40 Figure 4.6 UTS vs. Temperature................................................................................... 40 Figure 4.7 %El vs. Temperature ................................................................................... 41 Figure 4.8 %RA vs. Temperature ................................................................................. 41 Figure 4.9 s-e Diagrams vs. Environmental conditions................................................ 42 Figure 4.10 s-e Diagrams vs. Environmental conditions................................................ 43 Figure 4.11 CPP Diagram in 30ºC Acidic Solution........................................................ 45 Figure 4.12 CPP Diagram in 60ºC Acidic Solution........................................................ 45 Figure 4.13 CPP Diagram in 90ºC Acidic Solution........................................................ 46 Figure 4.14 CPP Diagram in 30ºC Acidic Solution........................................................ 46 Figure 4.15 CPP Diagram in 60ºC Acidic Solution........................................................ 47 Figure 4.16 CPP Diagram in 90ºC Acidic Solution........................................................ 47 Figure 4.17 Ecorr vs. Temperature ................................................................................... 48 Figure 4.18 Epit vs. Temperature..................................................................................... 49 Figure 4.19 s-e Diagrams vs. Cathodic Ecort ................................................................... 50 Figure 4.20 s-e Diagrams vs. Cathodic Ecort ................................................................... 50
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Figure 4.21 AppearancesofDCBSpecimensof Steel Containing 3 wt% Si..................... 52 Figure 4.22 Appearances of DCB Specimens of Steel Containing 4 wt% Si................. 52 Figure 4.23 Pictorial Views of Broken DCB Specimens................................................ 54 Figure 4.24 SEM Micrographs of Tensile Specimens of Steel Containing 3 wt% Si .... 57 Figure 4.25 SEM Micrographs of Tensile Specimens of Steel Containing 4 wt% Si .... 59 Figure 4.26 SEM Micrographs of SSR Specimens of Steel Containing 3 wt% Si......... 60 Figure 4.27 SEM Micrographs of SSR Specimens of Steel Containing 4 wt% Si......... 61 Figure 4.28 SEM Micrographs of Econt Specimens of Steel Containing 3 wt% Si ......... 62 Figure 4.29 SEM Micrographs of Econt Specimens of Steel Containing 4 wt% Si ......... 63 Figure 4.30 Fracture Morphology at Different Regions of Broken DCB Specimen ...... 64
ix
ACKNOWLEDGMENTS
I am extremely happy to take this opportunity to acknowledge my debts and gratitude
to those who were associated with the preparation of this thesis. Words fail to express my
profound regards from the inmost recess of my heart to my advisor Dr. Ajit Roy for the
invaluable help, constant guidance and wide counseling extended to me right from the
selection of the research topic to the successful completion of this thesis.
I am extending my sincere thanks to Dr. Anthony E. Hechanova, Dr. Daniel P. Cook,
and Dr. Edward S. Neumann, for their direct and indirect contribution throughout this
investigation. My colleagues from the Materials Performance Laboratory supported me
constantly in my research work. I want to thank them all for their help, support, interest
and valuable suggestions; I am especially obliged to Dr. Debajyoti Maitra, Pankaj
Kumar, Joydeep Pal, Ramashekar Koripelli, Dr. Arindam Ghosh, Vikram Marthandam
and Anand Venkatesh.
I would like to express my heartfelt gratefulness to my parents Mrs. Vijaya Laxmi
and Mr. Prabhu, my sisters Veena and Rama and my friends for their persistent support
and boundless confidence in me. Finally I would like to acknowledge the financial
support of the United States Department of Energy (USDOE).
1
CHAPTER 1
INTRODUCTION
The disposal of nuclear waste has been a major challenge to all nuclear power
generating nations. While the methods of disposal have been different in other countries,
significant efforts have been made in the United States to dispose of spent nuclear fuel
(SNF) and high-level radioactive waste (HLW) in a geologic repository located at the
Yucca Mountain site in Nevada for 10,000 years. Originally, this disposal site was
designed to accommodate approximately 77,000 metric tones of SNF/HLW already
generated from the existing nuclear power plants in this country. However, with times,
more and more nuclear wastes are being generated that would eventually need their
disposal at other locations. Therefore, the United States Department of Energy (USDOE)
had been considering numerous methods to enhance the efficiency of the proposed Yucca
Mountain repository so that both existing and future nuclear waste could be stored in this
repository for shorter durations. One such method is the transmutation of nuclear waste
that may enable minimization or elimination of radioactive species from these wastes so
as to store them for shorter durations without developing any additional disposal sites.
The process of transmutation consists of transformation of long-lived isotopes into
species with relatively shorter half-lives and reduced radioactivity through capture and
decay of minor actinides (MA) and fission products (FP) [1]. This objective can
accomplished by natural radioactive decay, nuclear fission, neutron capture and other
2
related processes. Transmutation involves bombarding a target material, such as tungsten
or molten lead-bismuth-eutectic (LBE) with accelerator-driven protons, causing the
generation of neutrons. This process of neutron generation is known as spallation that
may generate high operating temperatures ranging from 425-550oC. The generated
neutrons are then impinged upon SNF/HLW, producing MA and FP that can
subsequently be separated. The generation of MA and FP by the transmutation process is
illustrated in Figure 1.1.
Figure.1.1 Production of Fission Products and Minor Actinides
During the transmutation process, the structural material containing the target may
become susceptible to both stress-induced plastic deformation and environment-assisted
degradations such as stress-corrosion-cracking (SCC), hydrogen-embrittlement (HE), and
localized corrosion [2-4]. Thus, the determination of tensile properties and evaluation of
corrosion behavior of candidate target structural materials are necessary. At the inception
3
of the transmutation research program at UNLV, molten LBE was considered to be one
of the spallation targets for the next generation accelerator-driven-systems, producing
source neutrons and simultaneously acting as a blanket coolant during the spallation
process. However, corrosion testing in the presence of molten LBE could not be
performed due to the lack of proper testing infrastructures at UNLV. Therefore, extensive
corrosion studies involving several martensitic alloys have been ongoing at the Materials
Performance Laboratory (MPL) of UNLV in the presence of aqueous solutions [2-3]. The
results of numerous corrosion studies, performed at MPL, have been included in several
recent publications [2-5].
Martensitic stainless steels containing approximately 12 weight percent (wt%)
chromium (Cr) and 1 wt% molybdenum (Mo), known as 12Cr-1Mo steels, had been
extensively evaluated at MPL to determine their corrosion resistance in chloride-
containing aqueous solutions of varying pH values. These materials include Alloys EP-
823, HT-9 and 422. Of these alloys, Alloy EP-823, containing higher silicon (Si) content,
had been extensively used in Europe for transmutation applications due to its superior
corrosion resistance. In addition, this alloy possesses significant resistance to swelling
during high neutron exposure at temperatures up to 450oC, low rate of irradiation creep,
and rather low activation, compared to that of austenitic stainless steels [6]. Further, this
alloy has been reported to retain its high strength and ductility at elevated temperatures
even in irradiated conditions [5].
In view of the beneficial effect of higher Si content (1.14 wt%), observed [3] with
Alloy EP-823 in recent studies, a new investigation on the role of Si content on both the
metallurgical and corrosion properties of modified 9Cr-1Mo steel, also known as T91
4
grade steels, was initiated. These T91 grade martensitic steels contained Si ranging from
0.5 to 2.0 wt%. The susceptibility of these T91 grade steels of varied Si content to
environment-assisted-degradations had been extensively evaluated at MPL, the results of
which have been presented in a most recent publication [5]. Simultaneously, the
metallurgical properties evaluations including the development of a deformation
mechanism of these alloys under tensile loading at elevated temperatures had been
ongoing. Meanwhile, a recommendation was also made by researchers at the Los Alamos
National Laboratories to evaluate the effect of Si content in excess of 2 wt%, preferably
up to 4 wt% on the performance of Cr-Mo steels. In accordance with this
recommendation, a collaborative research effort was initiated to investigate both the
tensile properties and corrosion behavior of martensitic 12Cr-1Mo steels containing 3 and
4 wt% Si.
The current investigation is aimed at evaluating the tensile properties of two heats of
Si-containing 12Cr-1Mo steels at temperatures relevant to the transmutation process. In
addition, the susceptibility of these alloys to SCC, HE and localized corrosion has been
determined in the presence of an acidic solution at ambient and elevated temperatures.
Numerous state-of-the-arts experimental techniques have been employed to determine the
tensile properties, cracking tendency, and localized corrosion (pitting and crevice)
behavior of 12Cr-1Mo steels containing 3 and 4 wt% Si. Since the cracking susceptibility
of martensitic alloys can be significantly influenced by the generation of hydrogen
resulting from electrochemical reactions during operation, the role of applied cathodic
(negative) potential on the SCC behavior of these alloys has also been investigated.
Finally, the extent and morphology of failure of all tested specimens have been analyzed
5
by optical microscopy and scanning electron microscopy. The overall data generated
from this investigation, and their plausible explanations with respect to both the
metallurgical and corrosion aspects of 12Cr-1Mo steel have been presented in this thesis
as a function of the Si content.
6
CHAPTER 2
TEST MATERIALS, SPECIMENS AND ENVIRONMENT
2.1 Materials
The materials tested in this investigation were martensitic 12Cr-1Mo stainless steels
containing two levels of silicon (Si) content. The martensitic alloys have found extensive
use as containment materials in the transmutation systems in Europe and Russia due to
many desirable properties including excellent corrosion resistance, optimum tensile
strength and ease of manufacturing. Stainless steels possess excellent corrosion resistance
compared to that of other steels due to the presence of high chromium (Cr) content.
Simultaneously, the presence of high Si content has proved to be beneficial [5] from both
the metallurgical and corrosion aspects for numerous energy applications. The Cr-Mo
steels tested in this investigation have been known to perform satisfactorily due to their
stable metallurgical microstructures, high oxidation and sulphidation resistance, high
thermal conductivity and low thermal expansion, compared to that of the conventional
austenitic stainless steels. W and V have also been added to 12Cr-1Mo steels to enhance
their tensile properties and creep-rupture strength at elevated temperatures. The typical
tensile and physical properties of the tested materials are given in Tables 2.1 [7] and 2.2 [8]
respectively.
7
Table 2.1 Typical Tensile Properties of 12Cr-1Mo Steel
Table 2.2 Physical Properties of 12Cr-1Mo Steel
Density 7.6 gm/cc
Thermal Conductivity (λ) 27 W.m-1.K-1
Electrical Resistivity (ρ) 55x10-8 Ω.m
Thermal Expansion 11.2 X 10exp-6/°C
Specific heat 460 J/Kg °K
Two experimental heats of Cr-Mo steels were melted by a vacuum-induction-melting
(VIM) practice at the Timken Research Laboratory (TRL), Canton, Ohio. They were
subsequently forged and hot-rolled into plate materials of desired dimensions.
Subsequently, they were heat-treated prior to the machining of the test specimens. These
plates were austenitized at 1110oC (1850oF) for one hour followed by oil quenching, thus,
producing hard but brittle martensitic microstructures. In order to relieve the internal
stresses due to quenching, and homogenize the metallurgical microstructures, the
quenched materials were tempered at 621oC (1150oF) for one hour and air-cooled. This
type of thermal-treatment can usually lead to the development of fully-tempered
martensitic microstructures without the formation of any retained austenite. The chemical
compositions of the tested material are given in Table 2.3
Yield Strength ksi
Ultimate Tensile Strength, ksi
% Elongation % Reduction Area
110 139 13 30
8
Table 2.3 Chemical Compositions of Cr-Mo Steels Tested Elements (wt %) Heat
No. C Mn P S Si Ni Cr Mo Al V W N(ppm) Fe 2548 .18 .4 .005 .004 3.24 .5 12.36 1.01 .03 .312 .445 140 Bal
One example of the use of the uncertainty analysis is shown in this section. This can be
implemented to all experimental results discussed in this thesis.
E.2 Uncertainty Calculation for Parameters Derived from SSR and Econt Results
E.2.1 Calculation of Uncertainty in Time to failure (UTTF)
Filed Point Software of the SSR unit is used to obtain the TTF, which is accurate up
to 1/100th of a second in finding the TTF. Therefore, the uncertainty of the TTF in the
SSR testing is negligible.
E.3 Uncertainty Calculations for Parameters derived from CPP Results
The uncertainty of the potentiostat provided by the manufacturer is ± 0.003 mV
within a range of 1 mV.
Sample calculation:
For corrosion potential (Ecorr) = -497 mV
91
The uncertainty in Ecorr = -497*(±0.003) = ±1.491 mV
One example of the use of the uncertainty analysis is shown in this section. This can be
implemented to all experimental results discussed in this thesis.
92
BIBLIOGRAPHY [1] Transmutation., http://www.npp.hu/jovo/transzmutacio-e.htm National Research Council, Nuclear Wastes - Technologies for Separations and Transmutation, Washington, D.C., National Academy Press (1996) [2] Ajit K. Roy, Ramprashad Prabhakaran, et al., "Stress Corrosion Cracking of Nuclear Transmutation Structural Materials", Materials Performance, NACE International, , Vol. 43, No. 9, pp. 52-56, September 2004 [3] Ajit K. Roy and M.K. Hossain, “Cracking of Martensitic Alloy EP-823 Under Controlled Potential”, JMEPEG, Vol. 15, No. 3, pp. 336-344, June 2006 [4] A.K Roy, M.K. Hossain et al., “Environment-Assisted Cracking of Structural Materials under Different Loading Conditions”, Corrosion, pp. 364-370, April 2005 [5] Debajyoti Maitra, “Tensile Deformation and Environmental Degradation of T91 Grade Steels With Different Silicon Content”, Dissertation, August 2007 [6] A K Roy, Joydeep Pal, Chandan Mukhopadhyoy, “Dynamic Strain Ageing of an Austenitic Super alloy- Temperature and Strain Rate Effects”, et al., Materials Science and Engineering A 2007, in press [7] “Valve Magazine”, Vol. 13, No. 1, pp. 3, winter 2001 [8] R. K. Williams, R. S. Graves, and D. L. McElroy, “Thermal and Electrical Conductivities of an Improved 9 Cr-1 Mo Steel from 360 to 1000 K”, International Journal of Thermophysics, Vol. 5, No. 3, 1984 [9] ASTM Designation E8-2004, “Standard test methods for tensile testing of metallic materials”, American Society for Testing and Materials (ASTM) International. [10] NACE Standard TM0177-90, “Laboratory Testing of Metals for Resistance to Sulfide Cracking in H2S Environments” National Association of Corrosion Engineers, pp. 16-22 [11] A.K Roy, U. Valliyil and E. Govindaraj, “The Role of Applied Potential on Environment-Assisted Cracking of Zirconium Alloys”, J. of ASTM Int. Vol. 3, No. 4, April 2006
93
[12] R. Prabhakaran, A.K Roy, “Degradations of Type 422 Stainless Steel in Aqueous Environments”, Materials Science and Engineering A, Vol. 421, pp. 290-297, 2006 [13] Fast Track 8800, “Bluehill 2 Software”, Instron Material Testing Systems [14] Instron Testing Systems, “Specifications-Model 8862”, Dynamic and Fatigue Test Systems-High Precision Electric Actuator Systems [15] ASTM G5-94 (1999), “Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements,” ASTM International [16] A. K. Roy, et al., “Effect of Controlled Potential on SCC of Nuclear Waste Package Container Materials,” Proceedings of NACE Corrosion 2000, Paper No. 00188, Orlando, FL, 2000 [17] A.K. Roy, et al., “Stress Corrosion Cracking of Ni-Base and Ti Alloys Under Controlled Potential,” 7th International Conference on Nuclear Engineering, Paper No. ICONE-7048, Tokyo, Japan, April 19-23, 1999 [18] ASTM G129-00, “Standard Practice for Slow Strain Rate Testing to Evaluate the Susceptibility of Metallic Materials to Environmentally Assisted Cracking,” ASTM International [19] ASTM Designation E 399-1999, “Standard Test Method for Linear-Elastic Plain-Strain Fracture Toughness K1C of Metallic Materials,” American Society for Testing of Materials (ASTM) /international [20] A.K. Roy, D.L. Fleming, D.C Freeman and B.Y. Lum, “Stress Corrosion Cracking of Alloy C-22 and Ti-Gr-12 Using Double-Cantilever-Beam Technique”, Micron, Vol. 30, pp. 649-654, 1999 [21] NACE Standard Double-Cantilever-Beam Test, 1990, NACE Standard TM0177-90, Method D, NACE International, Houston, Texas, pp. 17-22 [22] Joydeep Pal, “Tensile Properties, Fracture Toughness and Crack-Growth Study of Alloy C-276,” M.S. Thesis, December 2006 [23] Ramashekar Koripelli, “Tensile Deformation, Corrosion and Crack-Growth Characterization of a Nickel-Base Alloy” Ph.D. Dissertation, December 2007 [24] A. K. Roy, S. Bandyopadhyay, S. B. Suresh, D. Maitra, P. Kumar, D. Wells, L. Ma, “Relationship of Residual Stress to Dislocation Density in Cold-Worked Martensitic Alloy,” Materials Science and Engineering A, Elsevier Science, Vol. 416, January 2006, pp. 134-138
94
VITA
Graduate College University of Nevada Las Vegas
Sreenivas Kohir
Address: 4213 Grove Circle, Apt # 1 Las Vegas, NV 89119 Degree:
• Diploma in Mechanical Engineering, 1999 SBTET, Hyderabad, India
• Bachelor of Engineering, Mechanical Engineering, 2005 CBIT, Osmania University, India
Professional Experience:
• Worked as Supervisor, Design and Production Dept. at Browne’s Engineering Pvt. Ltd., Hyderabad, India, Sep’99-Apr’00
• Assistant Process Engineer, Production Planning & Control Dept. at Denison Hydraulics Pvt. Ltd., Hyderabad, India, May’00-May’01
• Teaching Assistant at University of Nevada Las Vegas, Jan’06-Jan’07 • Research Assistant, University of Nevada Las Vegas, Jan’07-Present
Special Honors and Awards:
• Selected as a Tau Beta Pi (The Engineering Honor Society) Member in March 2007
• Board of Director, American Nuclear Society (ANS), UNLV Chapter, Nov’06-Present
• Secretary, Indian Student Association (ISA), UNLV, Jan’07-Present Selected Publications:
Ajit K. Roy, Sreenivas Kohir, “Effect of High Silicon Content on Martensitic Stainless Steels”, American Nuclear Society (ANS) Student Conference, March 2007, Oregon State University, Oregon, USA.
Ajit K. Roy, Sreenivas Kohir, “Tensile Properties and Environmental Degradation of Martensitic and Austenitic Stainless Steels”, International Symposium for Research Scholars (ISRS), December 2006, IIT-Madras, India.
95
Ajit K. Roy, D. Maitra, P. Kumar, Sreenivas Kohir, “Metallurgical and Corrosion Characterization of T91 Grade Steel versus Silicon Content”, ANS Student Conference, April 2006, RPI, New York, USA.
Thesis Title: Characterization of Martensitic Stainless Steels with High Silicon Content Thesis Examination Committee: Chairperson, Dr. Ajit K. Roy, Ph.D. Committee Member, Dr. Antony E. Hechanova, Ph.D. Committee Member, Dr. Daniel P. Cook, Ph.D. Graduate College Representative, Dr. Edward S. Neumann, Ph.D.