Tham khảo tài liệu 'advances in gas turbine technology part 17', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 470 Advances in Gas Turbine Technology Images of surfaces of blade specimens were acquired both before and after specimens soaking in the furnace. The photos were taken on a purpose-built workbench Bogdan Blachnio 2007 Blachnio Bogdan 2008 with a digital photo camera while the surfaces were illuminated with scattered white light. Repeatability of the obtained results was proved by taking multiple photos of the same specimens under the same conditions with appropriate settings of parameter of the digital photo camera. The soaking of blade specimens in the furnace led to alterations in colour of the surfaces. An exemplary set of images is shown in Fig. 7. Fig. 7. Images of surfaces of specimens soaked at various temperatures It was also determined how the temperature of blade soaking affects their microstructures. Examination was carried out using metallographic microsections and both an optical and a scanning electronic microscope SEM . Fig. 8 shows the new blade structure before soaking. One can see the coating of the aluminium alloy Fig. 8a diffused in the blade parent metal as well as cuboidal precipitates of the y phase of the alloy Fig. 8b . Fig. 8. Metallographic structure of the blade prior to soaking a coating magn. x450 b subsurface layer magn. x4500 The microstructures of high-temperature affected gas turbine blades were also observed. This provided detailed information about changes in the microstructures of both the coating layer alteration in the coating thickness and in the parent material. Changes in material parameters mainly modifications in the size and distribution of the Y phase substantially affect mechanical properties of the material Blachnio 2009 Decker Mihalisin 1969 Dudzinski 1987 Mikulowski 1997 Poznanska 2000 Sims et al. 1987 . Results of the examination of specimens subjected to soaking in the furnace at 1223 K and 1323 K are shown in Fig. 9 and Fig. 10 respectively. 471 New Non-Destructive Methods of Diagnosing Health of Gas Turbine .
