Perfectionnements apportés aux procédés pour l'établissement de pièces métalliques devant subir un traitement pour la formation d'au moins un alliage superficiel de diffusion, notamment à base de chrome

摘要

A sintered metallic piece is produced by carrying out at least the end of the sintering treatment in the presence of at least one fluoride. The piece may be formed by pressing metallic particles with or without binders and with or without a presintering heat treatment. the fluoride may be hydrofluoric acid and a metal which can form a diffusion alloy coating may be present in the reaction chamber. The reaction chamber may contain a metallic fluoride and hydrogen, the reaction between these substances and the metal of the piece produring hydrofluoric acid and a diffusion alloy coating on the piece. A slightly volatile fluoride may be mixed with the metal powder of the piece before sintering, and the piece may be supported in a granular mass of the metal of the fluoride vapour. Specification 693,292 is referred to.