Article ID Journal Published Year Pages File Type
769433 Engineering Failure Analysis 2009 11 Pages PDF
Abstract

Incorporation of Advanced High Strength Steels in structural parts of vehicles should save weight and enable economy of fuel. A very efficient protection against corrosion is achieved by hot-dip galvanization, which consists in dipping the steel in a molten zinc bath at a temperature around 450 °C. Degradation of the fatigue toughness of several steels after galvanization has been reported in several previous studies. Presently, we present new results concerning the evolution of mechanical properties of a silicon-rich TRIP800 steel after galvanization. The most striking is a reduction of endurance by a factor of ten at 525 MPa after galvanization. In the present work, we have ascertained two potential explanations for this degradation: (1) Modification of the core microstructure of the TRIP steel as a consequence of heat-treatment and (2) the propagation of cracks formed within the coating intermetallic layers after galvanization into the steel substrate upon cyclic loading. We found that heat-treatment is not responsible for the drop of fatigue lifetime. Our results neither provide any evidence that the cracks pre-existing in the zinc coating could be the starting point of the fracture in steel.

Related Topics
Physical Sciences and Engineering Engineering Industrial and Manufacturing Engineering
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