Method of removing a ceramic coating from a ceramic coated metallic article

A method of removing a ceramic coating from a ceramic coated metallic article, the metallic article having a first portion and a second portion, the first portion having a first metallic bond coating and a columnar grain ceramic coating applied to an oxide layer on the first metallic bond coating, and the second portion having a second metallic bond coating and a lamellae ceramic coating applied to a rough surface on the second metallic bond coating, the method comprising the steps of:

• a) immersing the ceramic coated metallic article in a caustic solution, the caustic solution comprising one of potassium hydroxide and sodium hydroxide;
• b) maintaining the ceramic coated metallic article in the caustic solution at atmospheric pressure for a predetermined time period and at a predetermined temperature;
• c) removing the ceramic coated metallic article from the caustic solution;
• d) rinsing the ceramic coated metallic article in water at ambient temperature;
• e) water jet blasting the first portion of the ceramic coated metallic article to remove the columnar grain ceramic coating by directing water at the columnar grain ceramic coating from a nozzle at a pressure of 275 to 296 MPa (40,000 to 43,000 psi), arranging the nozzle at a stand-off distance from the columnar grain ceramic coating of 25 to 35 mm and traversing the nozzle over the first portion of the metallic article at a speed of 4 to 6 mm per second;
• and
• f) water jet blasting the second portion of the ceramic coated metallic article to remove the lamellae ceramic coating by directing water at the lamellae ceramic coating from the nozzle at a pressure of 275 to 296 MPa (40,000 to 43,000 psi), arranging the nozzle at a stand-off distance from the lamellae ceramic coating of 30 to 40 mm and traversing the nozzle over the second portion of the metallic article at a speed of 5 to 8 mm per second,
• wherein the first portion and the columnar grain ceramic coating are located separately from the second portion and the lamellae ceramic coating, and
• wherein the water jet blasting of the second portion is carried out after the water jet blasting of the first portion so as to minimize erosion of the lamellae ceramic coating from stress waves.