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John Bohling

What is your thesis topic?
My dissertation research topic is focused on further understanding the creep behavior in 9Cr-1Mo-VNb (Grade 91) steels, specifically the occurrence of creep damage in the fine-grain weld heat-affected zone (FGHAZ or “Type IV” region).

How is materials processing involved in your research?
My research is concerned with the changes that occur in metals as a result of welding and heat treatment, primarily focused on carbon and low-alloy steels. The choice of welding process, specific welding parameters, and heat treatment conditions can dramatically alter the properties (such as strength and corrosion resistance) of a given steel. Thus, understanding the effects of welding on material properties is important to enable successful fabrication of steel structures and to either prevent or mitigate welding-related problems.

Provide an example of where the material/process/properties you are studying might find an application.
Cr-Mo steels are widely used in the power generation and petrochemical industries (e.g,. for steam piping in power plants. In welded Cr-Mo steel steam piping, the high temperature conditions lead to creep void formation in specific regions such as the FGHAZ or the weld deposit, eventually resulting in failure. Understanding how creep damage occurs in Cr-Mo steel weldments is important for determining when existing steam piping must be repaired or replaced and also for developing Cr-Mo steels with improved creep properties that enable power plants to operate at higher temperatures (and thus higher effciencies).