Steam turbine components with differentially coated surfaces

Method of erosion protecting a steam turbine component having plural fluid directing surface regions spaced apart and differently subject to solid particle impacts at angles ranging from below 20 degrees to above 30 degrees to the component surface as a reference plane, including interposing a first surface protection relatively less hard and relatively tougher than a second surface protection and comprising a chromium carbide thermal spray surface coating containing from 8 to 12% by weight cobalt or nickel binder on component surface regions where solid particle impacts are at angles above 30 degrees to the component surface, and interposing a second surface protection relatively less tough and relatively harder than said first surface protection and comprising a titanium boride or chromium boride diffusion alloy surface modification on other component surface regions where solid particle impacts are at angles below 20 degrees to the component surface, whereby said component is differently protected in different surface regions thereof as a function of the angle of attack of solid particles.

Steam turbine component having plural fluid directing surfaces exposed to erosive particle impingements at different angles of attack ranging from below 20 degrees to above 30 degrees relative to the component surface as a reference plane, a first surface protection comprising a thermal spray surface coating on component surfaces subject to particle impingements at less than 20 degrees to the component surface, and a second surface protection comprising a hard diffusion alloy surface modification on component surfaces subject to particle impingements at more than 30 degrees to the component surface, whereby differently particle-impinged surfaces of said component are differently protected.

Steam turbine component having plural fluid directing surface regions spaced apart and differently subject to solid particle impacts at angles ranging from below 20 degrees to above 30 degrees to the component surface as a reference plane, a first surface protection comprising a chromium carbide thermal spray surface coating containing from 8 to 12% by weight cobalt or nickel binder, said first surface protection being deposited on component surface regions where solid particle impacts are at angles above 30 degrees to the component surface, and a second surface protection comprising a titanium boride or chromium boride diffusion alloy surface modification formed in situ in said surface on other surface regions where solid particle impacts are at angles below 20 degrees to the reference surface, whereby said component is differently protected in different surface regions thereof as a function of the angle of attack of solid particles.