GENESIS AND EVOLUTION OF MICROSTRUCTURES IN SUPER DUPLEX STAINLESS STEEL: MORPHOLOGY AND PHASE TRANSFORMATIONS

Funding: CEMAM PhD fellowship (public sector)

Primary work place: SIMaP, St Martin d’Hères, Isère, France

Supervision: Prof. M. Veron (principal), Dr. H.P. Van Landeghem

Starting: 09/2016-10/2016

Super duplex stainless steel grades are modern stainless steel grades combining high specific mechanical properties with excellent corrosion resistance, especially to pitting corrosion. This association of desirable properties is achieved with great cost efficiency compared to other high performance alloys resisting extreme environments, such as nickel superalloys. The availability of super duplex grades enables the design of advanced systems and facilities in different field of applications including deep-sea oil and gas, desalination, automotive exhaust lines and more.

Like other stainless grades, super duplex contain chromium that grants them their stainless character, but also varying amounts of nickel and molybdenum to achieve their very specific microstructure. It consists in a mix of ferrite and austenite, usually at a 50/50 ratio, arranged in layers.

This microstructure controls the properties of the final alloy and as such, the path towards the optimization of current grades and the design of improved future super duplex grades is two-fold. On the one hand, it is necessary to know the exact dependence of the final properties on the ratio, the size and morphology of the phases. On the other, it is required to determine how these microstructural parameters can be controlled from an alloy-processing standpoint. While a companion PhD project will deal with the former aspect, the present PhD project will focus on the latter. It will involve the development of a thermo-kinetic computer model capable of quantitative prediction of the microstructure evolution as a function of processing variables. The performance of the developed model will be benchmarked using experimental data from industrial SDX2507 as well as from model microstructures designed and synthesized specifically for this purpose. Although this PhD is primarily concerned with modeling, it will thus involve experimental sample synthesis and microstructure characterization, at a provisional 65/35 ratio depending on the candidate.

The present PhD project will be hosted at the facilities of the laboratory SIMaP (science and engineering of materials and processes, simap.grenoble-inp.fr), member of the CEMAM (center of excellence for multifunctional architectured materials, cemam.grenoble-inp.fr). Both the current and companion projects will be co-supervised with our partner Aperam (www.aperam.com). Certain specific tasks will be performed externally in collaboration with our partners from CEA/Liten, Grenoble (E. Rigal) and McMaster University, Hamilton, Canada (H. Zurob). In this context, the candidate might have to travel abroad occasionally for up to a few months.

Applicants must hold a Master of Science degree or equivalent and must have a strong background in thermodynamics and phase transformations in metallic alloys. Knowledge of numerical methods is preferred. Knowledge of microstructural characterization techniques is also an asset. Applicants must be self-driven, highly motivated for graduate studies and able to work autonomously towards the objectives of the project.

Contacts:

·        Prof. M. Veron (muriel.veron@simap.grenoble-inp.fr)

·        Dr. H.P. Van Landeghem (hugo.vanlandeghem@simap.grenoble-inp.fr)