Reasons for embrittlement of a 10% Cr steel with high boron and low nitrogen contents

Significance 

Steels are widely used in various applications owing to their excellent physical and mechanical properties such as strength, toughness and ductility. Unfortunately, steels are susceptible to various failures resulting from causes like temperature changes that reduce their functionality and reliability. In a recently published literature, advanced 9-10% Cr steels with high boron and low nitrogen content were developed. These steels demonstrate an exceptional high-temperature strength making them favorable for critical application like power plants components. However, little emphasis has been given to the causes of embrittlement of high-chromium steels with high boron and low nitrogen content.

Recently, Dr. Roman Mishnev, Dr. Nadezhda Dudova, Dr. Valeriy Dudko and Professor Rustam Kaibyshev at Belgorod State University investigated the effect of lowering nitrogen and increasing boron content on ductile-brittle transition temperature of the 10% Cr steel under impact loading. They compared the results obtained with that for the P92-type steel chemical composition. Their work is published in the research journal, Materials Science and Engineering.

From the experimental results, the authors obtained a ductile-brittle transition temperature of 10°C. However, full embrittlement was obtained at a temperature of -80°C. Furthermore, lowering nitrogen content and increasing boron content resulted in an increase in the ductile-brittle transition temperature of the 10% Cr steel as compared to the conventional high-chromium steels like the P92-type steel. This was attributed to the high density of the carbides located at the boundaries that led to the formation of the voids and cracks.

The study successfully investigated the effect of low nitrogen and high boron in ductile-brittle transition temperature of the 10% Cr steel. For instance, resulting voids at the carbide-matrix boundaries produced a principal unstable crack with critical dimension after propagation of a stable crack on a very short distance. This led to low impact energy and embrittlement at relatively high temperatures. Therefore, the Belgorod State University scientists are optimistic that the study will advance the application of high-chromium martensitic steels for critical components in various dimensions. This will further help in component failure prevention.

Reasons for embrittlement of a 10% Cr steel with high boron and low nitrogen contents - Advances in Engineering

About the author

Roman Mishnev (https://www.researchgate.net/profile/R_Mishnev) is a Research Associate in the Laboratory for Mechanical Properties of Nanostructured Materials and Superalloys at Belgorod National Research University, Russia, since 2013 when he received his Engineer Diploma. Recently, in 2018, he received his PhD degree in the field of Metal Science and Heat Treatment from National University of Science and Technology «MISIS». His research interests are concerned with investigation of advanced heat-resistant high-chromium martensitic steels. His research is focused on creep and fatigue properties, impact toughness, microstructure, fractography, precipitates, transmission and scanning electron microscopy. His presentation on the long-term microstructural evolution in a 10% Cr high creep resistant martensitic steel at the International Conference on Advances in Materials Technology for Fossil Power Plants which was organized by the Electric Power Research Institute in 2016 was recognized as the best presentation. In 2017, he was awarded by Gold medal from Russian Academy of Science.

About the author

Nadezhda Dudova is a Leading Research Associate in the Laboratory for Mechanical Properties of Nanostructured Materials and Superalloys at Belgorod National Research University, Russia, since 2008. In 1999 she received her Engineer Diploma from Ufa State Aviation Technical University and, in 2009 she received her PhD degree in the field of Condensed Matter Physics from the Institute for Metals Superplasticity Problems. She is author of about 50 scientific papers.

She has experience in the deformation behavior and formation of ultrafine and nanocrystalline structure in nickel-based alloys under severe plastic deformation.

Her current research interests include mechanisms of microstructural changes under creep and fatigue conditions in high-chromium martensitic steels. Her major focus is on alloying of advanced high-chromium steels, heat treatment, mechanical characterization, creep and low-cycle fatigue, impact toughness, microstructure, phase transformation, dispersed precipitates.

About the author

Valeriy Dudko is a Senior Research Associate in the Laboratory for Mechanical Properties of Nanostructured Materials and Superalloys at Belgorod National Research University, Russia, since 2007. In 2004 he received his Engineer Diploma from Ufa State Aviation Technical University and, in 2014 he received his PhD degree in the field of Metal Science and Heat Treatment from National University of Science and Technology «MISIS», Moscow, Russia. He is author of about 27 scientific papers. He has experience in the deformation behavior and microstructure analysis of high-chromium martensitic steels.

His current research interests include mechanisms of microstructural changes under creep and fracture mechanisms in high-chromium martensitic steels. His major focus is on heat treatment, mechanical characterization, creep, impact toughness, microstructure, phase transformation, dispersed precipitates.

About the author

Rustam Kaibyshev is a Head of the Laboratory for Mechanical Properties of Nanostructured Materials and Superalloys at Belgorod National Research University, Russia, since 2007. He received his PhD degree in the field of Metal Science and Heat Treatment in 1991 and DrSci degree in the field of Condensed Matter Physics in 1995 from Moscow Institute for Steel and Alloys.

He is author of more than 400 papers. He is a member of Organizing Committees of several International Conferences, e.g., ICSAM, REX&GG, THERMEC, ICAA, ECCC. In 2018, he was awarded by “Professor of Year”, National Prize from Russian Professors’ Convention.

Research interests include wide range of materials such as metal matrix composite, martensitic and austenitic heat-resistant steels, aluminum, nickel and copper alloys. His scientific expertise incorporates creep and superplasticity mechanisms, dynamic recrystallization, microstructural design, evolution of ultrafine grains during severe plastic deformation, mechanisms of plastic deformation.

References

Mishnev, R., Dudova, N., Dudko, V., & Kaibyshev, R. (2018). Impact toughness of a 10% Cr steel with high boron and low nitrogen contents. Materials Science and Engineering: A, 730, 1-9.

Go To Materials Science and Engineering

Check Also

Aging resistant TiO2/silicone rubber composites - Advances in Engineering

Aging resistant TiO2/silicone rubber composites