| With the development of aviation manufacturing industry,research institutions all over the world have invested more and more in aviation engine research.As the core component of aero engine,how to extend its working life and durability is an important research content.The cooling film can form a protective air film on the surface of the turbine blade,which can isolate the blade from the high temperature of the combustion chamber,thus extending the working life of the turbine blade in a certain extent.There are usually hundreds of such holes on a blade,the diameter of which is usually between 0.2mm and 0.8mm.In processing processes,defects such as recast layer and heat-affected zone will be generated,which will lead to fatigue fracture of turbine blades and seriously affect the service life of turbine blades.A novel method of laser machining combined with high temperature chemical etching(LMHTCE)for gas film hole processing on the IN718 superalloy.This novel method can take full advantage of both approaches to drill film holes in an IN718 superalloy without a recast layer or a heat affect zone(HAZ).Firstly,the technology of gas film hole processing is introduced,and the advantages of LMHTCE and the specific processing process are explained in this thesis.It also explains the selection of the experimental platform and the corresponding equipment.Secondly,a solution of hydrochloric acid and sodium nitrate,which minimally reacts with IN718 at room temperature but rapidly reacts under high temperatures,was tested and chosen.In order to realize that the recast layer,thermal affected zone and other defects,can be completely removed by LMHTCE,the processing of laser in air,water and chemical solution was compared and studied,and the parameters such as laser power and defocusing amount were experimentally explored,and finally a hole without defect layer can be obtained which taper is about 0.11. |
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