Abstract: A bond coating material providing unexpectedly high thermal cyclic fatigue resistance and sulfidation resistance, and unexpectedly prolonged thermal cycle life in high temperature environments of gas turbine engine components with and without the presence of sulfur contains: a) 10% to 30% by weight chromium, b) at least one of tantalum and molybdenum in a total amount of 3% to 15% by weight, c) 5% to 13% by weight aluminum, d) 0.1% to 1.4% by weight silicon, e) 0.1% to 0.8% by weight yttrium, f) 0% to 1.2% by weight carbon, g) 0% to 1% by weight dysprosium, h) 0% to 1% by weight cerium, i) the balance being nickel, and the percentages of a) to i) adding up to 100% by weight. The total amount of tantalum and molybdenum, and the amounts of aluminum and silicon are each critical for avoiding delamination of a top coat from a bond coat.

Abstract: A thermal barrier coating (TBC) top coat which is a high entropy oxide (HEO) having a high configurational entropy, contains at least 5 different oxide-forming metallic cations, is a single phase or single crystalline structure, such as tetragonal or cubic over unexpectedly wide temperature ranges up to and beyond top coat operating temperatures of preferably at least 2300° F. The TBC top coats exhibit low thermal conductivity, good sintering resistance, excellent phase stability and good thermal cycling performance. At least five of the different oxide-forming metallic cations include: a) at least one of the transition metals: Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Ni, Cu, or Zn, and/or at least one of the lanthanides La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb. Dy, Ho, Er, Yb, or Lu. One of the at least five different oxide-forming metallic cations may also comprise at least one of the alkaline-earth metals: Be, Mg, Ca, Sr, or Ba.