Abstract: A process for reducing the coefficient of friction and the wear between a metal part and an organic polymer- or copolymer-based part, in an aqueous medium containing chlorides, characterized in that the organic polymer- or copolymer-based part is submitted to a surface treatment by ionic implantation of elements selected from nitrogen, argon, oxygen and carbon.

Abstract: The roll is made from a low alloy steel having the following composition by weight : C: 0.76 to 0.92; Mn: 0.70 to 1.40; Si: 0.70 to 1.40; S.ltoreq.0.020; P.ltoreq.0.025; Ni.ltoreq.0.60; Cr: 1.50 to 2.20; Mo: 0.15 to 0.55; V: 0.08 to 0.25; Cu.ltoreq.0.50; the remainder being iron and accidental impurities.

Abstract: A process for the chromization by gas of steels containing more than 0.2% of carbon, consisting of three successive treatments, the chromization treatment proper employing a cement having a ferrochrome base containing between 1% and 3% of carbon, and preferably 2%. The process is particularly useful in the chromization of structural and tool steels.

Abstract: The object of the present invention is an improvement in chromizing methods, constituted by a method of chromizing steels to a depth e greater than 30 microns, usable for steels with a carbon content of at least 0.2%, especially for steels for construction work and steels for tools, characterized by the combination of three successive treatments, the first of these three treatments consisting of an ionic nitriding of a surface layer between 100 and 350 microns thick, this ionic nitriding being realized in an atmosphere constituted by a mixture of nitrogen and hydrogen, at a temperature of between 450.degree. C. and 650.degree. C., for between 5 and 40 hours, so as to obtain between 1.5% and 2.5% nitrogen in the nitrided layer, the second of these treatments consisting of a chromizing by gaseous method forming chromium carbides, lasting between 5 and 30 hours, and realized at temperatures of between 850.degree. C. and 1,100.degree. C.