Powder Bed Fusion produced Haynes 282 Nickel-based superalloy: post deposition treatments and long-term thermal exposure behaviour characterization.

This project focuses on the characterization of Powder Bed Fusion - Laser Beam (PBF -LB) produced Haynes 282 Nickel-based superalloy. The microstructure of samples subjected to different post-deposition treatments was analysed through X-ray diffraction, optical and electron microscopy, with emphasis on the evolution of γ' hardening precipitates and carbides. The "CombiHIP" treatment, in which solution and two-step ageing is integrated into a single hot isostatic pressing cycle at different temperatures and holding times, made it possible to reduce the heat treatment time, improving efficiency. At the same time, it can help to reduce printing defects such as porosity and lack of fusion while reducing processing energy requirements. Long term thermal exposure (LTTE) treatments were performed for 500 h at 760 ºC, 850 ºC and 930 ºC to test the thermal stability of the CombiHIP processed material. Microstructural evaluation and high temperature tensile testing proved that the material held its properties after the exposure cycle at 760 ºC. On the other hand, after 850 ºC and ºC exposure, a significant coarsening of the precipitates was observed, which could have a negative effect on the mechanical properties of the material. Vickers hardness measurement validate this hypothesis, as the 760 ºC exposed sample maintained pre-exposure hardness while 850 ºC and 930 ºC showed a 10% decay. The results from this study indicate that PBF-LB can be used to produce high quality Haynes 282 parts, specially when combined with tailored heat treatments such as the proposed CombiHIP. LTTE cycles simulating working conditions show that the material properties remain consistent after 500 h at 760 ºC, with signs of degradation at 850 ºC and 930 ºC.