Gas turbine engines are employed in a variety of applications, such as aircraft, and marine vessels, among others. The gas turbine engines generate a thrust from a fluid flow by first compressing an intake air within a compression unit. The compression unit utilizes a series of bladed discs or bladed rings for compressing the intake air. The compression unit supplies the compressed air to be mixed with a fuel mixture for combustion in a combustion unit. The resulting hot, high pressure gaseous mixture is expanded through a turbine portion to extract energy which drives the compressors and a propulsor such as a fan or propeller. Energy may also be extracted in the form of electrical power.
The bladed discs are a unitary construction having a disc (or a drum) and a number of blades spaced apart from each other. If the disc and the blade are integrated as a single piece, weight saving may be achieved. As a result, non-mechanical methods of joining the blades have been proposed, wherein the bladed discs are machined from a single forged piece. However, such methods suffer from manufacturing challenges due to less efficient utilization of expensive materials and expensive forging machinery.
Due to technical challenges associated with a high temperature environment, the bladed discs are required to be fabricated with dissimilar materials. However, there are technical challenges in joining two dissimilar materials. For example, joining of the dissimilar materials, i.e. a blade and disc alloys having different crystal structures, differences in thermal processing (i.e. heat treatment) requirements and difficulty in joining using a solid state or melting processes, such as a fusion welding. Further, the fusion welding may give unfavorable post weld mechanical properties due to a heat affected zone and mixing of alloys, increased grain size and lack of post weld homogenisation heat treatment. Furthermore, the dissimilar materials have different characteristics, i.e. weld induced residual stress or optimum material condition (e.g. aging) and hence there are always challenges in joining the dissimilar materials. Furthermore, the welding procedures of the dissimilar materials may require large and costly setups. Therefore, there is a need for an improved bladed disc that is fabricated from the dissimilar materials and further a method of manufacturing the same is proposed.