The Interdiffusion Behavior of NiCoCrAlYHf Coating Deposited by Arc Ion Plating on Carburized Ni-Based Single Crystal Superalloy

In the present study, arc ion plating (AIP) was used to prepare a NiCoCrAlYHf coating (HY5 coating) on a carburized third-generation single-crystal superalloy DD10. The interdiffusion behavior of the carburized superalloy with an HY5 coating was investigated for a 1000 h oxidation time at 1100 °C. Carburization enhanced the interfacial bonding force and improved the microstructure of the NiCoCrAlYHf coating. An interdiffusion zone (IDZ) formed after a 300 h oxidation time, and the formation of a carburized layer effectively suppressed an inward diffusion of cobalt, aluminium, and chromium to the DD10 superalloy as well as an outward diffusion of nickel and refractory elements for instance rhenium and tungsten to the HY5 coating that occurred in static air at 1100 °C. The roles of the carburized layer in affecting thermal cyclic oxidation and element interdiffusion were studied. Subsequently, a modified form of the Boltzmann–Matano analysis was used to present the interdiffusion coefficients of aluminium.

Cyclic oxidation behaviour of ZrB2 -20 vol.%MoSi2 based ultra-high temperature ceramic matrix composite between 1100°C and 1300°C

While descending through different layers of atmosphere with tremendously high velocities, hypersonic re-entry nosecones fabricated using ultra-high temperature ceramic matrix composites (UHTCMCs) are subjected to repeated thermal shocks. This necessitates extensive investigations on the cyclic oxidation behaviour of UHTCMCs at temperatures ranging from 1100°C to 1300°C (service temperature of the nosecones). To this end, the present work is aimed at investigating the cyclic oxidation behaviour of ZrB2 -20 vol.%MoSi2 (ZM20) UHTCMC (a very widely investigated ZM CMC) by carrying out cycles for 6h, at 1cycle/h and estimating oxidation kinetic law. This has been followed by extensive characterisation using X-Ray Diffraction (XRD) to indicate the phases formed during oxidation and Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), in order to determine the chemical composition of the oxides formed between 1100°C and 1300°C.

High Temperature Oxidation Performance of an Additively Manufactured Mo–9Si–8B Alloy

As reported in previous studies, the processing of Mo–Si–B alloys using additive manufacturing (AM) techniques, like directed energy deposition (DED) shows a high technical feasibility. The present work investigates the cyclic oxidation performance of an AM DED Mo–9Si–8B alloy. Depending on the temperature (800 °C, 1100 °C, 1300 °C), the oxidation mechanisms vary, which is due to different reactions at the surface of the alloys accompanied with mass changes of samples. These mass changes can be explained on the basis of microstructural investigations. However, compared to a powder metallurgically processed Mo–9Si–8B alloy, the AM-DED alloy shows competitive oxidation performance at potential application temperatures of 1100 °C and 1300 °C, while a catastrophic materials degradation occurs at 800 °C as also observed in other Mo-rich Mo–Si–B alloys.