Volume 50, Issue 12

Electroplated thin-walled tubes were tested in compression. Most cracks were found at defects, i. e. protrusions on the surface of the tubes. The study focusses on the characterization of these defects. Optical microscopy revealed that the defects were already present in the metallization layer and occurred during the metallization process. When electrodepositing a Nickel coating on top, grains grow perpendicular to the surface of the metallization layer creating local orientation changes. Thus, protrusions occur on the surface of the tube where imperfections are located in the metallization layer. The results will be valuable for improving the deformation characteristics of the electrodeposited tubes; they can also be used to design new types of electrodeposits by patterning the substrate.

Metallic components manufactured via the Powder Metallurgy route require more attention in terms of adjusting the process parameters in order to control the chemistry during production. Therefore the first step towards a robust production through the Powder Metallurgy route is the characterization of the chemical features of the metal powder both on the surface and in the bulk. This review is an assortment of examples of characterization studies used for investigating different features observed in metallic powders.

An Iran Airlines CF6–80C2A2F engine had a turbine failure during takeoff from the Arlanda airport in Sweden, in January 2010. Failure investigation of the engine was performed by Lufthansa Technik AG (LHT). The Swedish Accident Investigation Board (SHK) requested a second opinion of the available High Pressure Turbine (HPT) Diffuser Aft Seal hardware, received from LHT, and because of GKN Aerospace Sweden's extensive experience as Original Equipment Manufacturer (OEM) of Swedish fighter engines this second failure analysis work was performed by GKN. The failure investigation of the Diffuser Aft Seal pieces and fragments received from LHT revealed no fractures or fatigue cracks which are believed to be evidences of the primary cause to the failure. However, a secondary fatigue crack was found in an aft tooth fragment from the Diffuser Aft Seal. This tooth fragment has also a machining step on the forward surface, between a repair weld and the original tooth, with a geometry which gives a stress concentration factor of about 2.5 for radial and bending stresses in this area. This machining step may have contributed to initiate a fatigue crack in the seal tooth.