Research Projects

The proposed work focuses on the development of molybdenum (Mo)-free duplex stainless steel (DSS) with high chromium (~32 wt%) and lean additions of tungsten (W), nitrogen (N), copper (Cu), and titanium (Ti), targeting a balanced ferrite-austenite microstructure and corrosion resistance equivalent to standard Mo-containing grades such as AISI 2205. The need arises from the high cost, strategic criticality, and processing limitations associated with Mo, including its role in promoting brittle intermetallic phases (sigma and chi), which compromise mechanical properties and manufacturability. The central hypothesis is that removing Mo and optimizing alloying with Cr, W, N, Cu, and Ti, can achieve comparable corrosion and mechanical properties through careful control of thermo-mechanical processing. The project aims to identify a processing window that prevents intermetallic formation, maintains phase balance, and avoids hot cracking. Thermodynamic CALPHAD modelling will guide alloy design by predicting phase stability and intermetallic formation. Alloys will be prepared through vacuum induction melting (VIM) and hot forged to homogenize the cast structure. Gleeble-based hot compression simulations will investigate deformation behaviour at various strain rates in the 950-1200 °C temperature range. Processing maps based on dynamic material modelling (DMM) will be developed to identify stable deformation zones. Additional intermediate annealing trials will be conducted to evaluate the precipitation behaviour of sigma and chi phases. The microstructural characterization will involve SEM, EBSD, and XRD to assess grain morphology, crystallographic texture, intermetallic formation, and ferrite-austenite phase fraction. Special focus will be given to Kurdjumov-Sachs (K-S) orientation relationships and their potential role in cracking during hot deformation. Mechanical properties will be evaluated by tensile and Charpy impact testing, including sub-zero impact tests, with fractography for failure analysis. Electrochemical methods, including potentiodynamic polarization, DL-EPR, and EIS in chloride-rich environments, will assess corrosion performance. FTIR and optical profilometry will analyze corrosion product formation and surface degradation. Laboratory-scale hot rolling trials will validate the optimized processing window. Post-rolling evaluation will include surface inspection, phase analysis, and mechanical and corrosion testing. The expected outcome is a Mo-free DSS alloy with validated processing parameters suitable for applications requiring corrosion resistance and formability. The results will contribute to reducing dependence on imported Mo, lower alloy costs, and improve sustainability through reduced embodied carbon. The project also addresses knowledge gaps in texture evolution and its link to cracking in high-Cr DSS systems. It establishes a composition-processing-property framework applicable for further alloy development.