Abstract: The process with a view to imparting to the treated article a resistance to frictional wear, a corrosion resistance, and a color, is characterized according to the invention in that the surface of the article is subjected to a thermochemical pretreatment under electric plasma in a vessel under an atmosphere containing reactive species such as N.sub.2 and hydrogen, the reactive species diffusing into and precipitating in the metal matrix of the article to form a diffusion sublayer and in that a layer of carbon in vapor phase is deposited under electric plasma on the surface thus treated, in the same vessel, the composition of the atmosphere for the pretreatment being gradually modified, on the one hand, by the introduction of a hydrocarbon and/or of a silane in the gaseous state and, on the other hand, by progressive reduction of the partial pressures of the reactive species employed during the pretreatment, and the maintenance of the hydrocarbon atmosphere for the carbon deposition.

Abstract: The object of the present invention is a deposition process of a coating of the ceramic type based on carbides, nitrides, or carbonitrides of metallic elements such as Cr, V, Zr, W, Mo, Co, Mn, Ni, Hf, Ta, Ti, Nb and Fe in which the coating of the ceramic type is deposited at low temperature in the vapour phase on a metallic substrate from organo-metallic precursors wherein, prior to this deposition in the vapour phase and without subsequent placing in contact with an oxidizing and/or polluting atmosphere, a reactive ionic pickling is carried out in a reducing atmosphere.

Abstract: The object of the invention is a one-step deposition process of a coating of the ceramic type based on nitrides or carbonitrides of at least one metallic element selected from Cr, V, Zr, W, Mo, Co, Mn, Ni, Hf and Ta on a metallic or ceramic substrate, massive or obtained from fibres, by deposition in the vapor phase wherein a coating is deposited on the substrate by a chemical means at a pressure lower than 10 kPa at a temperature lower than 600.degree. C. and by using a system of precursors constituted simultaneously of:an organo-metallic precursor of the said metallic element selected from the organo-metallic compounds of the sandwich type of general formula:[Ar.sup.1 M Ar.sup.2.sub.n ]L.sub.x L'.sub.ya nitrogen precursor selected from ammonia and hydrazine.

Abstract: The present invention relates to a ferrous article suitable for use in devices for burning heavy and extra heavy petroleum fuels and a process for forming such an article. The article has a matrix formed from a low carbon steel and a corrosion resistant chromium-aluminum diffusion coating on at least one surface. The coating is formed by subjecting the matrix to successive aluminization and chromization pack cementation treatments.

Abstract: The present invention relates to a ferrous article suitable for use in devices for burning heavy and extra heavy petroleum fuels and a process for forming such an article. The article has a matrix formed from a low carbon steel and a corrosion resistant chromium-aluminum diffusion coating on at least one surface. The coating is formed by subjecting the matrix to successive aluminization and chromization pack cementation treatments.