Structural component with a protective coating having a nickel or cobalt basis and method for making such a coating

A method for protecting a structural component made of a nickel or cobalt base metal composition having a first crystal orientation, with a protective coating, consisting of the following steps:

• (a) applying a preliminary surface treatment to said structural component by removal of a surface layer from said structural component to form a coating surface for improving a bonding strength,
• (b) directly coating said coating surface of said structural component by means of plasma spraying with a plasma spray material having a chemical composition which is exactly identical to said base metal composition for forming said protective coating having a grain structure which is at least one thousand times more fine grained than said base metal composition,
• (c) solution annealing at temperatures between 1150.degree. C. and 1250.degree. C. for causing an epitaxial recrystallization in said protective coating so that a second crystal orientation in said protective coating is the same as said first crystal orientation in said base metal composition, and
• (d) aging said structural component with its protective coating by maintaining said structural component at a temperature within the range of 1080.degree. C. to 1120.degree. C. for two to six hours, cooling said structural component to a temperature within the range of 750.degree. C. to 800.degree. C., and then maintaining said structural component within a temperature range of 900.degree. C. to 980.degree. C., for ten to twenty hours for forming a .gamma./.gamma.' texture, wherein diffusion is avoided.

A method for protecting a structural component made of a nickel or cobalt base metal composition having a first crystal orientation, with a protective coating, comprising the following steps:

• (a) applying a preliminary surface treatment to said structural component by removal of a surface layer from said structural component to form a coating surface for improving a bonding strength,
• (b) coating said coating surface of said structural component by means of plasma spraying with a plasma spraying with a plasma spray material having a chemical composition which is exactly identical to said base metal composition for forming said protective coating having a grain structure which is at least one thousand times more fine grained than said base metal composition,
• (c) solution annealing at temperatures between 1150.degree. C. and 1250.degree. C. for causing an epitaxial recrystallization in said protective coating so that a second crystal orientation in said protective coating is the same as said first crystal orientation in said base metal composition,
• (d) aging said structural component with its protective coating by maintaining said structural component at a temperature within the range of 1080.degree. C. to 1120.degree. C. for two to six hours, cooling said structural component to a temperature within the range of 750.degree. C. to 800.degree. C., and then maintaining said structural component within a temperature range of 900.degree. C. to 980.degree. C., for ten to twenty hours for forming a .gamma./.gamma.' texture, wherein diffusion is avoided, and
• (e) after-treating the surface of said protective coating by applying a diffusion coating selected form the group consisting of aluminum and chromium, to said protective coating.