Method of forming a silicon diffusion and/or overlay coating on the surface of a metallic substrate by chemical vapor deposition

摘要

The invention relates to a method of forming a silicon diffusion and/or overlay coating on the surface of a metallic substrate comprising the steps of introducing the sample into a cold wall Low Pressure Chemical Vapor Deposition (LPCVD) enclosure, evacuating the enclosure up to a pressure P₁ which is lower than 0.5 Torr, maintaining said pressure P₁ while heating up said sample to a temperature which is comprised between about room temperature and about 300°C, bringing under same pressure P₁ the sample to the CVD temperature comprised between about 50°C and 1000°C, introducing a gas or gas mixture comprising at least one silicon hydride gas, maintaining the pressure inside the enclosure between about 0.1 and about 100 Torr, maintaining the introduction of said gas or gas mixture in the enclosure for deposition and/or diffusion of silicon on and/or through the surface of said metallic sample to obtain the desired thickness of the silicon diffusion and/or overlay coating, cooling down the sample to about room temperature and withdrawing said sample from said LPCVD enclosure. The substrate is preferably polished to obtain a mirror finish and then cleaned, either mechanically or chemically, with a solvent, or both.