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Steel for a fossil-free future
Luleå University of Technology
Co-financed by Swedish Agency for Economic and Regional Growth
With funding from the EU

Kaiyang Zeng

Developing hydrogen tolerant steels also requires addressing many materials characterisation challenges - including how to measure the location of H atoms. These challenges in scientific measurement and theory are what interests Kaiyang

Kaiyang Zeng
Kaiyang Zeng PhD student

What were you doing before joining Steel for a Fossil-Free Future?

I studied nanotechnology at KTH and completed my master’s thesis at the Department of Micro and Nanosystems focusing on device design for bacteria separation from blood for sepsis diagnosis. Shortly after graduation, I joined Steel for a Fossil Free Future project and continued my academic research and study within the field of materials science and engineering.

What will you be doing as a PhD student?

As a PhD student, I will be doing research on the hydrogen embrittlement behavior of Cr-Ni-based austenite stainless steel. This will encompass identifying the embrittlement or strengthening behavior related to the evolution of different microstructures and defects during/after the tensile testing of the steel after H charging. Subsequently, it will come up with a new steel design to tackle the embrittlement problem caused by hydrogen in various steel applications like hydrogen storage tanks, automotive industrials, etc.

What challenges will your PhD work contribute to solving?

There are three main challenges in the research:

  1. To tackle the characterization limitation to study H atoms/clusters in the steel because H has low scattering cross-section by electrons and X-ray. This can increase the difficulties to explain crack initiation and martensitic transformation quantified by hydrogen segregation when using EBSD and X-ray diffraction.
  2. To control the diffusion of H into/out of the steel. For austenite stainless steel, it will be difficult to introduce hydrogen atoms into the steel at atmospheric pressure and room temperature during H charging. To preserve H inside the steel after charging, temperature needs to be controlled during tensile testing or H characterization.
  3. To address the complications in characterization setup. For example, in atom probe tomography (APT) which can characterize H, a cryogenic workflow would be a very sensitive step to keep H atoms inside a nano-sizes tip. In neutron scattering, in-situ setups like tensile testing, heating or cooling, and H charging can become important considerations for a more deep-in study.

How can your research contribute to addressing those challenges?

My contribution is to utilize ex-situ electrochemical charging methods to introduce H into the austenitic stainless steel and perform mechanical testing subsequently. The cracked samples will be analyzed by SEM and EBSD to identify embrittlement-sensitive and embrittlement-resistant features compared with the non-charged samples. DICTRA module can help predict the diffusion of hydrogen into the depth of steel. Thermal desorption spectroscopy (TDS) and APT can help quantitatively establish the patterns of H segregation in the matrix and defects. With a thorough systematic study, a new steel design can be devised assisted by Thermo-Calc. It would be interesting to establish a collaboration in steel production using hydrogen for such designed hydrogen-embrittlement-resistant steel.

Find out more

My research project is called "Advanced characterization to detail the effects of hydrogen on mechanical properties of Fe-Ni-based austenitic stainless steel and developing strategies to design hydrogen-embrittlement-tolerant steel". Find out more here .