Self-Healing Concept To Improve The Mechanical Performance Of Vitreous Enamel Coated Steel

Nanoparticles of alumina were introduced in a blue enamel widely used to protect heat exchanger components, and the enamel was used to coat sheets of a low carbon steel. The composite structures were investigated in order to evaluate both the enamel-to-steel adhesion and the capability of the nanoparticles to allow a self-mending effect against deep brittle crack propagation phenomena within the enamel. The mechanical behaviour and crack sensitivity of steel samples coated using enamels both with and without additions of nanoparticles of alumina were submitted to impact load and bending tests and then analysed by means of different techniques to comparatively evaluate extent and morphology of the mechanical damages. It is shown that the addition of nanoparticles of -Al2O3 allows the enamel coating to display better mechanical performance in terms of increased post-elastic behaviour under bending condition, as well as of improved adherence and reduced spalling tendency under impact load conditions. The morphological differences between nanomodified and standard specimens at the steel-enamel interface are pointed out and discussed with reference to their effects on adhesion.