Mechanical testing of a selective laser melted superalloy

Selective laser melting is an additive manufacturing technology where metal powder is melted by a laser source layer-wise, forming a solid, dense metallic component. With the selective laser meting process, near net shape components can be manufactured directly from a 3D-model. The model is sliced into thin layers and a powder is spread onto a build platform. In the next step, the powder is fused by a laser as dictated by the model. The laser energy is intense enough to permit full melting (welding) of the particles to form solid metal. The process is repeated layer by layer until the part is complete. A number of materials are available, including steel, aluminium, titanium and, in recent time, also superalloys. The material investigated in the current project is a nickel base superalloy composition-wise equivalent to Hastelloy X, a solution strengthened superalloy typically used in large welded components exposed to high temperatures in oxidizing as well as reducing environments. Microstructurally, the material is different from both a hot-rolled, as well as a cast material due to the manufacturing process. Since the SLM process involves laser melting of powder particles in the size range of <50μm, the structure resembles of a weld structure, however on a smaller scale. Due to the layer-by-layer build strategy, the material will exhibit anisotropy. In the current project, high temperature mechanical fatigue and creep tests are performed. The microstructure is evaluated and the influence on the mechanical properties is discussed. Anisotropy in mechanical properties is discussed and the underlying factors of the anisotropy are analyzed