Laser powder bed fusion of advanced submicrometer TiB2 reinforced high-performance Ni-based composite

The Ni-based Hastelloy X (HX) superalloy is widely used in aero-engine components because of its exceptional high-temperature strength and oxidation resistance. Given the complex structure of such parts, additive manufacturing (AM) technologies such as laser powder bed fusion (LPBF) are employed to manufacture these components. HX alloy suffers from crack susceptibility during the LPBF process, however. In this paper, this issue was addressed by adding 2 wt% submicrometer TiB2 powder through a high-speed mixing process. Both the low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs) were noted to have increased in the as-fabricated HX-2 wt.% TiB2 composite, with an average grain size reduction from 14 μm to 8.69 μm. In addition, compared with pure HX, the hardness of the HX-2 wt.% TiB2 composite was increased by 43.4% and 50.8% at room-temperature and high-temperature (850 °C) conditions, respectively. This indicates that the added TiB2 reinforcement was more influential to the mechanical property enhancement under high-temperature compared to the room temperature conditions. The composite sample also showed a 28% increase in yield strength while the ductility was not found to be sacrificed compared to the as-fabricated pure HX, indicating that an addition of specific ceramic particles with suitable content may offer a new method for manufacturing crack-free high-strength and high-toughness HX alloy through the AM process. These findings also provide a reference for improving the properties of other advanced materials made by the LPBF process.