AUSTANDING: Lean austenitic stainless steel composite microstructure with enhanced mechanical properties

Extended project summary:

Additive manufacturing (AM), also known as 3D printing, based on layer-upon-layer building, is continuously proving itself to be a groundbreaking technology shaking metallurgists into the design of new alloys and complex microstructures, and, likewise, mechanical engineers into the conception of optimized parts. Heat exchangers are among the applications which most benefit from AM, as it enables the manufacturing of geometries otherwise impossible as a single part. The need of operation within a wide range of temperatures in corrosive environments might make the selection of austenitic stainless steels preferable over other alloys, owing to their superior stability. However, a disadvantage of stainless steels with respect to their competitors is the poor thermal conductivity of the former. Wall thickness reduction resulting in a better thermal transfer between fluids is limited by the strength-to-weight ratio of the corresponding material. Additionally, an appropriate ductility of AM-produced stainless steels is a clear prerequisite for high-pressure tubes and vessels.

With such a motivation, the AUSTANDING project aims to design a new AM-manufactured austenitic stainless steel, in particular using selective laser melting (SLM), following these strategies: high nitrogen content, and a mechanical composite behaviour conferred by an engineered sandwich-like microstructure. In this sense, the increase in content of critical chemical elements such as nickel will be avoided, resulting in an improvement in terms of sustainability. Computing tools based on thermodynamics and crystallography will be used for an optimum design.

Figure. Austenitic stainless steel