Coatability of IN718 components made by means of Selective Laser Melting (SLM)
Christopher Schaak, Institute of Materials Engineering, TU Dortmund, Dortmund, GermanyWolfgang Tillmann, Institute of Materials Engineering, TU Dortmund, Dortmund, GermanyMehmet Esat Aydinöz , Lehrstuhl für Werkstoffkunde (Materials Science), University of Paderborn, Paderborn, GermanyMirko Schaper, Lehrstuhl für Werkstoffkunde (Materials Science), University of Paderborn, Paderborn, Germany
Selective Laser Melting and other additive manufacturing (AM) processes have recently attracted large interest of researchers as well as the manufacturing industry. Especially the new freedom of design leads to completely new possibilities and fosters new ideas that lead to entirely new products. In the Selective Laser Melting (SLM) process the components are produced layer-wise by a laser beam. SLM is a powder bed based AM process and is characterized by the complete melting of the utilized powder material. Employing SLM, complex three-dimensional parts and light weight structures can be produced directly from 3D-CAD data.
Although SLM is a very promising technology, there are still some challenges to be solved. One aspect is the microstructure, as the microstructure of SLM parts differs from the microstructure of parts made by means of conventional processes like casting thus sometimes leading to differing mechanical properties. Other influences of SLM on mechanical properties are high residual stresses, the remaining porosity, and a high surface roughness. Coating processes normally need an adjusted surface treatment prior to their application. The respective surface treatment, such as grit blasting or surface finishing, depends on the coating process to be used. Furthermore, residual stresses in the substrate influence the adhesion of coatings and can lead to delamination, especially in case of thin coatings.
In the conducted experiments, two widely used coating processes, Cathodic Arc Deposition (Arc-PVD) and High Velocity Oxygen Fuel Spraying (HVOF) were used to coat components made by means of SLM with Ni-based IN718 coatings. The experiments show that the HVOF process can be used without an additional surface pretreatment, whereas the Arc-PVD process needs a thermal pre-treatment and a surface finishing.