Testing and evaluation of component made using electron beam melting and Alloy 718 powder

University essay from Mälardalens högskola/Akademin för innovation, design och teknik; Mälardalens högskola/Akademin för innovation, design och teknik

Abstract: The aerospace industry is constantly striving to becoming more economical and environmentally friendly. One of many efforts to achieve this is the Lightcam project which in this case is evaluating the use of additive manufacturing in the form of electron beam melting in conjunction with the nickel-based superalloy, Alloy 718. This combination is not fully explored and examined. For this purpose, a demonstrator vane was produced and it was subsequently evaluated in this thesis. The evaluation was performed in as-built condition and was divided in non-destructive testing, evaluation of these methods and metallographic review to confirm the results, and potentially revealing more properties. The non-destructive testing was performed using conventional radiography and computed tomography. Both methods struggled to deliver complete and reliable results, for varying reasons. Radiography could deliver results of the whole vane, but these were impossible to evaluate due to the rough surface created by the electron beam melting process. The computed tomography on the other hand was not affected by the rough surface and produced usable, though not complete, results of the vane. The reason for the computed tomography’s inability to deliver complete results was the material, varying thickness and complex geometry of the vane. As a complement and to verify the results from the non-destructive testing, a metallographic examination was conducted. These tests were conducted with the aim of answering the following three questions:  What non-destructive testing methods are suitable to evaluate Alloy 718 components manufactured with electron beam melting? - Neither radiography nor computed tomography are suitable as a sole evaluation method, for various reasons. All surface dependent methods were deemed unsuitable without testing due to the rough surface. What types of defects and in what quantity can they be found in the produced vane? - Defects found are: Porosity and lack of fusion, both found as internal and partially external and in varying sizes. Where are the defects located? - Pores are mainly found in the center of sections modeled to a 3mm thickness. Lack of fusion was found between build layers in all thicknesses. Apart from these results, hardness was found to vary depending on build height, increasing from the bottom towards the top. Microstructure was also found to vary with the build height, but always consisting of either equiaxed or columnar grains. 

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