Metal 3D printing as a disruptive technology for superalloys

illustration of solid mechanics with the solid state transformation thermal fluid dynamics and particle dynamics

Professor Roger Reed FREng, Dr Yuanbo T Tang of the Department of Materials, Oxford, and Dr Chinnapat Panwisawas now of the University of Leicester, have published their method for efficient manufacture of super alloys in Nature Communications.

Superalloys (a family of metal mixes based on nickel, cobalt or iron) have the durability and strength required by engine manufacturers, but have been notoriously diffcult to manufacture efficiently.  

Professor Reed, Dr Tang and Dr Panwisawas have developed a method of using 3D printing, or additive manufactoring (AM) instead of investment casting, which allows processing with reduced manufacturing steps and minimum processing waste.  

A laser-based melting and consolidation of solid powder approach with CAD opens new design possibilities (for example hollow structures or floam-like or lattice-based architectures), and a more effective use of materials in an additive, as opposed to subtractive, method.  Additionally, the AM process, with its melting and re-melting of fine powder size in micron length and time scale, leads to high cooling rates of 103 - 1060C/s and a very different metallurgical response to processing.

Solidification gives rise to a very fine celluar rather than dendritic microstructure, which virtually eliminates the dendritic segregation found in conventional processing, removing the need for a chemical homogenisation step, and suppressing precipitation by the severe cooling rate.  The precipitation phase can be optimised by designing new heat treatment protocols to obtain desirable microstructures associated with high strength in AM superalloys.