Influence of Minor Alloying Element Additions on the Crack Susceptibility of a Nickel Based Superalloy Manufactured by LPBF

Inconel 738LC (IN738LC) is a nickel-based superalloy specially used in the hot section components of turbine engines. One of its main drawbacks relies on the cracking susceptibility when it is manufactured by laser powder bed fusion (LPBF). This paper analyzes the influence of minor alloying element concentration on cracking tendency of IN738LC superalloy manufactured by LPBF. For that objective, samples were manufactured using two powders, which presented different minor alloying elements concentration (Si, Zr and B). It was shown that the samples crack tendency was very different depending on the powder used for their manufacturing. In fact, the measured crack density value was 2.73 mm/mm2 for the samples manufactured with the powder with higher minor alloying elements concentration, while 0.25 mm/mm2 for the others. Additionally, a special emphasis has been put on elemental composition characterization in cracked grain boundaries in order to quantify possible Si or Zr enrichment. It has been also studied the differences of solidification ranges and grain structures between both samples as a consequence of different minor alloying elements concentration in order to analyze their effect on crack susceptibility. In this sense, Scheil-Gulliver simulation results have shown that samples with higher Si and Zr contents presented higher solidification range temperature. This fact, as well as an increase of the presence of high angle grain boundaries (HAGB), leaded to an increment in the crack formation during solidification. Therefore, in this research work, an understanding of the factors affecting crack phenomenon in the LPBF manufactured IN738LC was accomplished.This research was funded by the Elkartek Programme, Grant Number KK-2020/00042

Strain sensitive conductive polyurethane foam/graphene nanocomposites prepared by impregnation method

Se prepararon nanocompuestos de espuma de poliuretano conductores mediante la incorporación de flakes de grafeno. Los flakes de grafeno se obtuvieron a partir de grafito por el método de exfoliación líquida en N metilpirrolidona y se seleccionaron por tamaño mediante centrifugación. Se realizó una caracterización en profundidad de los flakes de grafeno para comprender su rol como nanoentidades en la matriz de espuma de poliuretano. Así, la morfología, con especial énfasis en el número de capas, se analizó mediante espectroscopia Raman, microscopia de fuerza atómica y microscopia electrónica de transmisión. La microscopía de fuerza electrostática se utilizó para verificar la naturaleza conductora de los flakes de grafeno. Esta técnica demostró ser eficaz para evaluar tanto la morfología como las propiedades conductoras de los flakes de grafeno. En cuanto al comportamiento eléctrico de los nanocomposites de espuma, se determinó que la resistencia eléctrica depende tanto del contenido de grafeno como de la deformación por compresión aplicada al material.Poliuretano-aparraren nanokonposatu eroaleak prestatu ziren grafeno xaflak gehituz. Grafeno xaflak grafitotik abiatuta lortu ziren, N-metil pirrolidona bidezko esfoliazio likidoaren aplikatuz, eta tamainaren arabera banatu ziren zentrifugazio bidez. Grafeno xaflen karakterizazio sakona egin zen, poliuretano-aparraren matrizean nanoentitate gisa duten eginkizuna hobeto ulertzeko. Horrela, xaflen morfologia Raman espektroskopia, indar atomikozko mikroskopia eta transmisio elektronikozko mikroskopia bidez aztertu zen, geruza kantitatean arreta berezia jarriz. Indar elektrostatikoko mikroskopia grafeno xaflen izaera eroalea egiaztatzeko erabili zen. Teknika hori eraginkorra izan zen grafeno xaflen morfologia eta propietate eroaleak ebaluatzeko. Apar nanokonposatuen portaera elektrikoari dagokionez, erresistentzia elektrikoa grafeno-edukiaren eta materialari aplikatutako konpresio bidezko deformazioaren araberakoa zela ondorioztatu zen.Gobierno Vasco Grupos Consolidados (IT 776 13) Universidad del País Vasco / Euskal Herriko Unibertsitatea (PIFUPV047/2011