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Surface Crack Removal by EDM for Inside Cooling Hole of Gas Turbine Blade  

강신호 (한전기공주식회사 G/T 정비센터)
김대은 (연세대학교 기계공학과)
Publication Information
Journal of the Korean Society for Precision Engineering / v.20, no.8, 2003 , pp. 54-61 More about this Journal
Abstract
The first stage rotating blade of industrial gas turbine is one of the components that is normally run in exposed state at the highest temperature of the combustion gas stream. For this reason superior materials and advanced cooling technology are required to allow higher heat resisting characteristics of the component. The 1st stage blade of a selected commercial gas turbine blade made of directionally solidified Ni-based superalloy has a row of cooling holes on its trailing edge. In most cases, minor cracks have been found at some of the root cooling holes after one cycle operation (24,000 hrs) or even shorter operation time because of the high temperature gradient and the frequently alternating thermal stress. In the repair process, unfortunately, it is usually very difficult to get rid of the damage due to the fact that cracks are initiated at the root cooling hole and propagated deep into the hole. In this study, the feasibility of removing the sidewall cracks in the hole by utilizing EDM drilling has been investigated. Also the criteria of surface integrity for EDM drilling were established to achieve high quality repair as well as machining accuracy.
Keywords
Electrical Discharge Machining; EDM Drilling; Ni-based Superalloy; Surface Integrity;
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