Aplicación del ajuste de Rietveld para correlacionar la evolución microestructural de fundiciones blancas con 18 y 25% en Cromo, templadas en aceite y sucesivos revenidos, con el comportamiento frente al desgaste abrasivo y esfuerzos de flexión

Abstract

Through the application of Rietveld’s structural refinement method, the phases present in oil quenched and successively tempered treatments at 500 ºC of hypoeutectic white cast irons containing 18 and 25%-wt. Cr were identified. The former were correlated to the behavior shown under abrasive wear testing and bending testing too. The fraction of retained austenite after quenching for both highly alloyed irons was low. The alloy containing 18%-wt. Cr showed the highest fraction of carbides after quenching, and yet it was observed that secondary carbides seemed to develop preferentially in former destabilized proeutectic austenite as compared to former destabilized eutectic austenite. On the other hand, the highly alloyed cast iron with 25%-wt. Cr exhibited a more homogeneous phase resulting from austenite transformation after tempering. It was also observed that the cast iron containing 18%-wt. Cr showed partial solution of M7C3 carbides and a transformation of mixed secondary carbides of the M7C3 y M2C types. The fraction of martensite from quenching was detected to have a positive response to the resistance to abrasive wear, and illustrating of the inadequacy of quenching in oil for this sought property. The alloy bearing 25%-wt. Cr was found to have the highest martensite fraction after quenching, and thus a higher abrasive wear resistance. After a double tempering treatment, under bending testing, it displayed the highest rupture stress and strain, yielding a fragile fracture with facets of the transgranular mode. It was however observed the presence of regions depicting ductile fracture associated to double tempered martensite