The Attempt To Assess The Technical Condition Of A Gas Turbine Blade When Information On Its Operating Condition Is Limited

The paper discloses a non-invasive method of visual inspection based on processing of images taken for blade surfaces in the spectrum of visible light and then analyzed with the use of a computer-aided technology. The method of computer-aided analysis of images for blade surfaces is presented in details along with the obtained outcome, whilst the results from metallographic investigation of the blade superalloy are disclosed as well. The comparison is made between the results obtained from the analysis of images for blade surface and the results from the metallographic investigation of their structures. Finally, the relationship is established between parameters of digital images taken for surfaces of gas turbine blades in the visible spectrum of electromagnetic waves and microstructural parameters of the turbine blade metal. The completed investigations and analyses reveal that troubleshooting of gas turbine blades, which employs digital processing of images taken for its surface, offers new opportunities to determine the condition of blades after a long-term impact of a working agent at high temperature.

Metallographic Investigation on Solder Creep Phenomenon

Solder bulging is detected on the exposed paddle of Device A after burn-in causing the affected units to fail the coplanarity criteria. The affected units show up at random burn-in board socket locations and occur with varying frequency. Potential causes are plotted through an Ishikawa diagram which reveal fusion and creep as the potential mechanisms behind the solder bulging phenomenon. This paper seeks to determine the mechanism behind the solder bulging phenomenon via a 2-step metallographic investigation through (i) material deformation characterization and (ii) deformation mechanism simulation. In material deformation characterization, visual inspection on affected units show that the solder bulge is generally circular and is located on the center of the exposed paddle. Moreover, SEM/EDX analysis reveal that the solder bulge is not caused by a foreign contaminant or a compositional anomaly in the solder plating. On the other hand, deformation mechanism simulation involves the metallographic comparison between controlled simulations of fusion and creep versus the actual unit with solder bulge. Metallographic inspection reveal that the grain size and grain shape of the solder bulge possess the characteristics of creep phenomenon. Additionally, investigation on the burn-in (BI) process conditions also supports creep over fusion as the mechanism behind the solder bulging phenomenon. The static stress induced by the socket on the package at elevated temperature caused the solder plating to creep towards the free area which is the hole on the bottom of the socket.

METALLOGRAPHIC INVESTIGATION INTO THE ALUMINOTHERMIC WELDING OF RAIL JOINT R65 / R65 TIPO BĖGIO TERMITINIO SUVIRINIMO JUNGTIES METALOGRAFINIS TYRIMAS

The article describes inherent defects to aluminothermic welds, the origin of reasons and the ways of avoidance. The paper presents visual surface and fracture testing of rail joint R65 applying the method of aluminothermic welded joints. Santrauka Straipsnyje nagrinėjami galimi termitiniu būdu suvirintų jungčių defektai, jų atsiradimo priežastys ir nurodomi būdai, kaip jų išvengti. Atlikti R65 tipo bėgių termitiniu būdu suvirintų jungčių vizualiniai paviršiaus ir lūžio tyrimai.