Main damages on upper die in industrial hot forging Glavne ... - RMZ

456 Lavtar, L., Terčelj, M., Fazarinc, M., Kugler, G.Figure 1. Upper die after 45 766 strokes; two impressions for penultimateforging operation and two impressions for the last forging operation withmandrelsance to thermal fatigue, gross cracking,hot wear and plastic deformation. It isused for dies in die casting, hot forging,and hot extrusion. [14]Figure 2. Shape of steering mechanism afterthe last hot forging operationDie was gas nitrided and taken outof industrial process after its servicetime. Die was sectioned and examinedwith light microscopy (OlympusGX51) and by Vickers microhardnessmeasurements (Leitz Miniload 2). Diesurface was examinated using macroand micrograph techniques to revealsurface <strong>damages</strong> of nitrided layer. Additionally,metallographic examinationsof samples taken from certaincross-sections were performed. Nitaletchant for metallographic preparationof nitrided samples was used.RMZ-M&G 2010, 57