In this study, IN625 and a NiCrAlY coated IN625 were tested in high density and low density supercritical water for 500 h. The NiCrAlY coating was applied using plasma spray method. The surfaces were finely polished before testing to assist microstructure observation after testing. The NiCrAlY coated samples were additionally heat treated in air furnace to encourage alumina formation. SEM and XRD analyses were carried out to determine surface microstructure changes, particularly oxide formation. The results showed that when tested under high density supercritical water, the bare IN625 sample suffered from intergranular attacking while low density supercritical water did not have the same effect. Both as‐sprayed NiCrAlY and heat treated NiCrAlY did not show any signs of intergranular attack or pitting after being tested in high density and low density supercritical water.

Modern superalloys have enabled high pressure turbine (HPT) blades in gas turbine engines (GTE) to operate at higher temperatures. Unfortunately, the complexity of these materials can make it difficult to understand the failure mechanisms of these blades. HPT blades made of the nickel-based superalloy Mar-M002 have been found to suffer from stress assisted grain boundary' oxidation (SAGBO) cracking. HPT blades removed from an RB21I-24C aeroderivative industrial GTE were sectioned, atul the cracks and microstructure were studied using scanning electron micro.icopy (SEM) and energy dispersive X-ray spectroscopy (EDS). No cracks were found on the external surface of the blade, which had been coated with an oxidation resistant material. Surface irregularities were found along the walls of the inner cooling channels throughout the entire blade. Larger SAGBO cracks were observed to be near the lower 25% span of the blade and had initiated from the surfaces of the cooling channels. SEM/EDS analyses showed that these cracks had large amounts of alumina and hafnium-rich particles within them. It is evident that these cracks occurred in locations where the combination of high stress and high temperature led to higher rates of oxygen diffusion and subsequent oxidation of grain boundary' carbides. Hafnium carbide precipitates along the grain boundaries e.xpanded as they converted into hafnium oxide, thus further increasing the stress. It is envisaged that this increase in stress along the grain boundary has caused the cracks to initiate and coalesce. Based on this observation, it is believed that the inner cooling channels of these HPT blades could benefit from the application of cm oxidation resistant coating in order to prevent or delay the formation of these cracks.

Modern superalloys have enabled High Pressure Turbine (HPT) blades in Gas Turbine Engines (GTE) to operate at higher temperatures. Unfortunately the complexity of these materials can make it difficult to understand the failure mechanisms of these blades. HPT blades made of the nickel based superalloy Mar-M002 have been found to suffer from Stress Assisted Grain Boundary Oxidation (SAGBO) cracking. HPT blades removed from an RB211-24C aero-derivative industrial GTE were sectioned and the cracks and microstructure were studied using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). No cracks were found on the external surface of the blade which had been coated with an oxidation resistant material. Surface irregularities were found along the walls of the inner cooling channels throughout the entire blade. Larger SAGBO cracks were observed to be near the lower 25% span of the blade and had initiated from the surfaces of the cooling channels. SEM/EDS analysis showed that these cracks had large amounts of alumina and Hafnium-rich particles within them. It is evident that these cracks occurred in locations where the combination of high stress and high temperature led to higher rates of oxygen diffusion and subsequent oxidation of grain boundary carbides. Hafnium Carbide precipitates along the grain boundaries expanded as they converted into Hafnium Oxide, thus further increasing the stress. It is envisaged that this increase in stress along the grain boundary has caused the cracks to initiate and coalesce. Based on this observation, it is believed that the inner cooling channels of these HPT blades could benefit from the application of an oxidation resistant coating in order to prevent or delay the formation of these cracks.

Development of net-zero energy house (NZEH) optimization has resulted in NZEHs with much lower building costs. However, a viable pathway to cost-effective NZEHs has not yet been made evident. This study uses the Non-domination Sorting Genetic Algorithm II with active Pareto-archiving (aNSGA-II) and Iterated Sequential Search (ISS) algorithms connected with EnergyPlus to perform energy and cost optimizations on seventeen scenarios to determine how NZEHs can become more cost-effective and what is necessary to make them as or more cost-effective than code-built houses. Three house types are optimized in Ottawa, Ontario: a single detached house, an end unit townhouse and a middle unit townhouse. This research finds that a single detached NZEH can be cost-effective if occupant engagement is pursued, if the price of solar photovoltaics decreases to $1.434/W installed, and if the construction costs are similar to that of a large-scale developer.