The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 21, 1996
Filed:
Jul. 22, 1994
Hocine Hadj-Rabah, Saint-Etienne, FR;
Jean-Paul Terrat, Saint-Etienne, FR;
Centre Stephanois de Recherches Mecaniques Hydromecanique et Frottement, Andrezieux-Boutheon, FR;
Abstract
In a nitriding method intended to confer upon ferrous metal parts, in addon to surface properties resulting directly from nitriding, corrosion resistance comparable to that obtained when the nitriding treatment is followed by an oxidizing treatment, in particular in a salt bath, the parts are treated by immersion for an appropriate time in a molten salt bath containing in the known manner essentially alkali metal carbonates and cyanates and a small quantity of a sulfur-containing substance. The parts are held at a positive potential relative to a counter-electrode in contact with the bath so that a high current flows through the bath from the parts to the counter-electrode and the concentration of cyanides formed by secondary reaction is kept below 6%. It is preferable to use a constant average current; the typical current densities are from 300 amperes to 800 amperes per m.sup.2, the typical temperature ranges are from 450.degree. C. to 650.degree. C. and the typical treatment times are from 10 minutes to 150 minutes.