Abstract
The βNiAl coating was deposited onto Nickel based CMSX-4 superalloy by in-situ CVD (Chemical Vapor Deposition) method. Main focus of this contribution was to study the influence of aluminizing time and temperature on the microstructure and thickness of the coating; this was followed by examination by XRD (X-Ray Diffraction), electron microscope. Results suggest that an incremental variation in temperature alters the coating activities from HA (High Activity) to LA (Low Activity). This is exhibited by the resultant CT (Coating Thickness) since HA coatings are thicker than LA counterparts. The microstructure of the coating formed at low temperature (or HA ones) showed a large amount of α-Cr precipitates while one formed at high temperature (or LA ones) exhibited lower amounts of such precipitates. Moreover, incremental aluminizing time showed linear trend of CT at initial stage, thereafter (10 hrs) it leveled off. Whereas it does not affect microstructure of the coating
Highlights
BC (Thermal Barrier Coating) is applied ontoTturbine blades of aeroengine as to reduce their surface temperatures and enhance engine working efficiency
In-situ CVD method was used in present study to examine the effect of aluminizing conditions on microstructure and CT
A great number of aluminide coating samples were magnificently prepared onto single crystal CMSX-4 superalloy substrates
Summary
For BC to serve in TBC system its CT plays vital role since it provides aluminum reservoir for protection This is due to fact that the higher it is, the more is Al content that is instrumental for improved oxidation. This is mandatory in two ways; first the coating microstructure is substrate dependent that relies on coating formation parameters and second the turbine blades thickness is ~ 1mm, higher CT could deteriorate super alloy mechanical properties [7,8]. Interestingly in this research it was found that the temperature could change the process activities without changing the pack chemistry. At higher temperature, extended process time will be detrimental for the mechanical properties of superalloy components without significant increase in CT
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