Multilayer coating for high stressed metal pieces

Abstract

The multilayer coating for a metal piece, in particular a turbomachinery component, more in particular a turbomachinery impeller, comprising a first layer which is applied on at least a portion of the metal piece and which has a hydrogen diffusion coefficient of less than 10−7 m2/s even when subjected to stress (the hydrogen diffusion coefficient being measured through a hydrogen permeation test), and a second layer which is applied on top of the first layer and which is exposed to a process fluid comprising hydrogen. The second layer comprises an oxide chosen between: aluminum oxide (Al2O3), titanium dioxide (TiO2) and silicon dioxide (SiO2). The first and the second layer and may be applied according to various depositing process techniques at temperature below 500° C.

Dependencies are inferred from the claim text.