Microstructural analysis of a HP 40Nb alloy aged

Abstract

In this paper, the change in the microstructure of the centrifugally cast heat-resistant alloys of HP40 Nb after exposure to 0.5h and 2h of ageing times at 1123K and 1323K were investigated. The microstructures of the as-received alloy and aged conditions were examined using light microscopy (LM) and scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS). The chemical composition of various phases and precipitates observed in the aged sample microstructure was characterized by the means of scanning electron microscopy SEM via backscattered electron (BSE). The present results indicate that ageing enhanced the occurrence of different phenomena such as the transformation of primary M7C3 to M23C6 carbides and precipitation of secondary M23C6 carbides. It can be summarized that the present phases and the morphology of secondary carbides in the microstructure of aging results in higher values of hardness.