MODELIZATION OF THE STRESS DISTRIBUTION BY

FERNANDO BUEZAS; MARTA ROSALES; WALTER TUCKART

Buenos Aires

Workshop; 2º INTERNATIONAL WORKSHOP OF TRIBOLOGY TRIBAIRES 2013; 2013

Asociación Argentina de Tribología

Chromium coatings are widely used for industrial extreme applications due to their improved hardness and wearability at high temperature of engineering tools and several components. However during the chromium plating process, hydrogen is incorporated into the deposit forming chromium hydrides that are partially decomposed to metallic chromium and hydrogen gas. From this, the volume changes and promotes microcracking. Typically, the microcracks show a preferential orientation perpendicular to the substrate and they are distributed throughout their depth, could not be related to any special feature of the substrate, and none of them communicate the surface with the substrate. As observed by M. Gines et al. [1], the crack density diminishes when the bath temperature increases. It is worth to mention that microcracks density and distribution strongly depend on the bath chemistry. The microcracks density can range from 4000 cracks/mm2, and ~15 mm up to 14000 cracks/mm2, and ~7 mm (See Fig. 1). This condition is important for the wear resistance performance [1, 2] The objective of this work is the modelization of effect by friction on the stress distribution of perpendincular cracks intrinsically developed in hard chromium electrodeposited coatings. The influence of different sizes and density of cracks are evaluated and compared to a non-cracked coating.