Surface preparation process for deposition of ceramic coating
AssigneeUnited Technologies Corporation
InventorsRaymond P. Ristau, Sudhangshu Bose, Alan D. Cetel
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Abstract
A method of surface cleaning and controlled oxidation of superalloys is described. The method provides a thin homogeneous layer of relatively pure alpha alumina which is suited to receive and adhere to a subsequent vapor deposited coating.
Claims2
A method of preparing a superalloy substrate to receive a ceramic thermal barrier coating, without an intermediate bond coat, said superalloy being nickel base, containing 0.1-0.9% by weight of at least one element chosen from the group consisting of Y, Hf, Ce, La and mixtures thereof and containing sufficient Al to produce a predominately alumina surface film at elevated temperatures, said method including the steps of:
- a. degreasing said superalloy substrate;
- b. abrasively cleaning said superalloy substrate;
- c. ultrasonically cleaning said superalloy substrate;
- d. washing said substrate in an aqueous bath containing a wetting agent;
- e. rinsing said substrate at least once;
- and
- f. heat treating said substrate in an atmosphere that is non reactive with said substrate, non reactive with alumina, and which has a dew point of from about −30° F. to about −50° F. at a temperature and time sufficient to form a surface alumina layer which is predominately alumina and which has a thickness of from about 0.5 to 1.5 microns.
A method of preparing a superalloy substrate to receive a ceramic thermal barrier coating, without an intermediate bond coat, said superalloy being nickel base, containing 0.1-0.9% by weight of at least one element chosen from the group consisting of Y, Hf, Ce, La and mixtures thereof and containing sufficient Al to produce a predominately alumina surface film at elevated temperatures, said method including the steps of:
- a. degreasing said superalloy substrate;
- b. abrasively cleaning said superalloy substrate;
- c. ultrasonically cleaning said superalloy substrate;
- d. washing said substrate in an aqueous bath containing a wetting agent;
- e. rinsing said substrate at least once;
- f. rinsing said substrate in an aqueous organic solvent or aqueous solution of said solvent which dries without leaving a residue;
- g. drying said substrate;
- and
- h. heat treating said substrate in an atmosphere that is non reactive with said substrate, non reactive with alumina, and which has a dew point of from about −30° F. to about −50° F. at a temperature and time sufficient to form a surface alumina layer which is predominately alumina and which has a thickness of from about 0.5 to 1.5 microns.
Dependencies are inferred from the claim text.