Influence of heat treatments of annealing and destabilizing in precipitation of secondary carbides and in hardness of a white cast iron alloy high chromium with niobium

ABSTRACT

This study evaluates the effect of association annealing and destabilizing heat treatments in precipitation and morphology of secondary carbides and hardness in a high-chromium white cast iron alloy with the addition of niobium. White cast iron is used in the manufacture of components involving wear requests, mainly in the mining industries, in equipment such as ore transport chutes, due to its high hardness and high strength to abrasive wear. The heat treatments aim to improve the mechanical properties, through the precipitation of secondary carbides and the obtaining of martensitic matrices. The addition of chromium in cast irons aims to form carbides and increase the hardness of the alloy. The methodology used was the casting of the material with the addition of 0.5% niobium as an alloying element and metallographic characterization by means of optical and electronic microscopy techniques, as well as the quantification of carbides and performance of hardness tests. Destabilized samples were analyzed without and with previous annealing and it was verified that the annealing favored a greater precipitation of secondary carbides M₇C₃, allowing a reduction in the thermal treatment time of destabilization and the transformation of the austenitic matrix into martensitic during the cooling, promoting an increase in hardness.

Keywords
High chromium white cast iron; Secondary carbides; Annealing; Destabilizing; Hardness