This PhD project aims to understand and mitigate oxide formation at the interface of Grade 91 steels joined by hot isostatic pressing (HIP)-assisted diffusion bonding.

This process offers significant potential for manufacturing complex components for the future DEMO nuclear fusion reactor.

However, the formation of oxides, particularly silica (SiO2), at the bonding interface can weaken the joints and significantly reduce their impact toughness.

The main objective is to identify the physicochemical parameters governing oxide formation at high temperatures.

The study will focus on the effects of silicon and manganese contents, temperature, and oxygen partial pressure.

Model alloys and Grade 91 steel will be investigated experimentally under controlled atmospheres.

Experimental findings will be compared with thermodynamic simulations based on the CALPHAD method.

HIP-bonded joints will then undergo multiscale microstructural characterization and mechanical testing.

Optimization strategies, including surface preparation and degassing conditions, will be assessed to minimize interfacial oxidation.

The expected outcomes include a reliable bonding procedure that can be transferred to EUROFER 97 steel and potentially applied to other industrial sectors.