Heat checking patterns and their relation to oxidation on a tool steel containing second-phases particles

Abstract:

Thermal fatigue tests were carried out in a tool steel containing sec-ond-phase particles. The aim of this work was to investigate and understand the nucleation mechanisms of thermal fatigue and the formation of the crack networks on the surface in specimens subjected to thermal cycles similar to those suffered by hot forming tools like hot rolling rolls. For this, we looked in greater detail for the surface characteristics during the early stages of cracking and for the microstructure close to the surface. Static oxidation and thermal fatigue tests were performed. In the end, it is concluded that the mechanisms for the appearance of a first secondary crack network, restricted to the oxide layer, and a main crack network, which leads the material to failure, are distinct but related. First network formation accelerates the nucleation of main cracks by the appearance of preferential stress concentration and oxidation sites. The carbides play an important role in the nucleation of both types of cracks, by formation of interfaces and concentration of stresses.


Reference:

BRAGA, Ana Paola Villalva; LIMA, Luiz Gustavo Bianchi da Silva; SOUZA, Roberto; PEREIRA FILHO, Mario Leite; BOCCALINI JUNIOR, Mario. Heat checking patterns and their relation to oxidation on a tool steel containing second-phases particles. In: INTERNATIONAL TOOLING CONFERENCE, 11., 2019, Aachen, Alemanha. Proceedings… 8 p.

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