Methods for preparing thermal barrier coatings with high fracture toughness inner layer for improved impact resistance

A method comprising:

• providing a thermal barrier coating on an underlying metal substrate by:
• a) forming an inner high fracture toughness layer overlaying the metal substrate, the inner layer having a fraction of porosity of about 0.20 or less, and a thickness in the range of from about 0.5 to about 2 mils, and sufficient to impart impact resistance to the thermal barrier coating, the inner high fracture toughness layer comprising a zirconia-containing ceramic composition having a c/a ratio of the zirconia lattice in the range of from about 1.011 to about 1.016 and stabilized in the tetragonal phase by a stabilizing amount of a stabilizing metal oxide selected from the group consisting of yttria, calcia, ceria, scandia, magnesia, india, lanthana, gadolinia, neodymia, samaria, dysprosia, erbia, ytterbia, europia, praseodymia, and mixtures thereof, and wherein the inner high fracture toughness layer comprises from about 0.3 to about 0.5% by weight of a metal oxide selected from the group consisting of lanthana, neodymia, gadolinia, and mixtures thereof, and
• b) forming an outer thermal insulating layer overlying the inner layer and comprising a ceramic thermal barrier coating material.

A method for preparing a thermal barrier coating for an underlying metal substrate, the method comprising the steps of:

• a) forming an inner high fracture toughness layer overlaying the metal substrate, the inner layer having a fraction of porosity of about 0.20 or less, and a thickness in the range of up to about 5 mils, and sufficient to impart impact resistance to the thermal barrier coating, and comprising a zirconia-containing ceramic composition having a c/a ratio of the zirconia lattice in the range of from about 1.011 to about 1.016 and stabilized in the tetragonal phase by a stabilizing amount of a stabilizing metal oxide selected from the group consisting of yttria, calcia, ceria, scandia, magnesia, india, lanthana, gadolinia, neodymia, samaria, dysprosia, erbia, ytterbia, europia, praseodymia, and mixtures thereof, and wherein the inner layer comprises from about 2 to about 7% by weight hafnia, and wherein the inner layer comprises from about 0.3 to about 0.5% by weight of a metal oxide selected from the group consisting of lanthana, neodymia, gadolinia, and mixtures thereof, and
• b) forming on the inner layer an outer thermal insulating layer adjacent to and overlying the inner layer and comprising a ceramic thermal barrier coating material.

A method for preparing a thermal barrier coating for an underlying metal substrate, the method comprising the steps of:

• a) forming an inner high fracture toughness layer overlaying the metal substrate, the inner layer having a fraction of porosity of about 0.20 or less, and a thickness in the range of up to about 5 mils, and sufficient to impart impact resistance to the thermal barrier coating, and comprising a zirconia-containing ceramic composition having a c/a ratio of the zirconia lattice in the range of from about 1.011 to about 1.016 and stabilized in the tetragonal phase by about 4 to about 7% by weight of a stabilizing metal oxide selected from the group consisting of yttria, calcia, ceria, scandia, magnesia, india, lanthana, gadolinia, neodymia, samaria, dysprosia, erbia, ytterbia, europia, praseodymia, and mixtures thereof, and wherein the inner layer includes at least one of hafnia or a metal oxide selected from lanthana, neodymia, gadolinia, and mixtures thereof, wherein if present, the hafnia is present in from about 2 to about 7% by weight, and wherein if present, the metal oxide is present in from about 0.3 to about 0.5% by weight;
• and
• b) forming on the inner layer an outer thermal insulating layer adjacent to and overlying the inner layer and comprising a ceramic thermal barrier coating material.