Boruration des aciers et cermets : le traitement « Borudif »

Application of the « borudif » boriding-process to steels and cermets

Equipe Céramiques Spéciales et Traitements de Surface, Ecole Nationale Supérieure des Mines, Saint-Etienne.

Abstract

A steel bonding process (Borudif) is described which is based upon the moderated activation (BF₃ and SiO₂) of boron carbide B₄C. On carbon steels this technique has the advantage of forming a single phase acicular layer of Fe₂B. It may also be applied to alloy steels and cermets. There is no adhesion between the reactants and the treated components, giving a better surface finish, no wasting of the powder ; the possibility of gaseous phase bonding improves the surface finish. The costs are five times less in raw materials than directly competitive methods. Analytical, physico-chemical (X-ray, metallography, electron probe analysis, glow discharge spectroscopy) and mechanical investigations (micro-hardness, torsion, traction, bend and wear tests) were performed to characterize the nature, composition, morphology and adherence of the bonded layers.

Boronized steels may be used for all components requiring frictional wear resistance, molten salts (cryolite). Our process is competitive with other boronizing, chromising, nitriding... technics.