Fatigue behaviour of selective laser melted Hastelloy X

Over the past ten years rapid prototyping of metallic materials has gained an increased interest from the industry. Improved methods for manufacturing of components by laser deposition and progress within understanding of metallurgy have enabled use of steels, titanium and even cobalt- and nickel-base superalloys in laser sintering manufacturing. However, understanding of anisotropy, damage mechanisms and material response to cyclic loads is not well-known.

The current paper is focussing on the damage development of a solution strengthened superalloy produced by additive manufacturing, more precisely laser bed additive manufacturing. For the current work, the alloy Hastelloy X was selected. Hastelloy X is a well-known alloy which is frequently used in stationary gas turbine applications, mainly in burners, combustor liners and hot gas path heat shields. In the extreme environment found in the gas turbine combustor / hot gas path, the alloy is exposed to conditions imposing mechanical and creep damage into the material simultaneously as the material is being degraded by oxidation and corrosion.

In the present research, the fatigue behaviour at high temperature is reviewed by performing thermomechanical fatigue of test bars machined from additive manufactured material. The test bars are machined in order to evaluate the bulk properties. Testing has been conducted in the temperature regime where creep plays an important role in the damage development. The fatigue properties and behaviour is addressed and compared to traditionally manufactured material. Differences in damage mechanisms are highlighted. Influence of creep is discussed and fractography results are presented.