Phase evolution within multiphase stainless steels during simulated hot isostatic pressing cycles

Stainless steel hardfacing alloys are being developed for wear and corrosion resistant applications in pressurised water reactor environments. Two examples of this, the austenitic Tristelle 5183 and triplex RR2450 were produced by gas-atomisation before undergoing consolidation using hot isostatic pressing. The phase evolution of these alloys during simulated hot isostatic pressing cycles was observed in-situ , using synchrotron X-ray diffraction. During these cycles, the metastability of the gas-atomised powders is revealed, which influences the rate of high-temperature gamma -> delta transformation within the RR2450 alloy. Additionally, a high-strength silicide phase, named pi-ferrosilicide, forms within these alloys. It decomposes by a eutectoid pi -> delta+M7C3 transformation, demonstrating a high carbon solubility within this phase. The observations of this study demonstrate the need to carefully consider the process parameters during hot isostatic pressing for such complex alloys, since alloy phase transformation rates are heavily influenced by the starting condition of the gas-atomised powder.

Automated summary

This study investigates the application of stainless steel hardfacing alloys in pressurised water reactor environments and observes the phase evolution of these alloys during hot isostatic pressing cycles using synchrotron X-ray diffraction. The results demonstrate the importance of considering the starting condition of the gas-atomised powder in the hot isostatic pressing process, as it heavily influences the alloy phase transformation rates.