Patent ID: 7186092

Claim:
A turbine airfoil having a leading edge, a trailing edge, a convex curved surface suction side extending from the leading to the trailing edge, and a concave curved surface pressure side extending from the leading to the trailing edge, the pressure side having a leading edge portion aft of the leading edge and trailing edge portion forward of the trailing edge, the turbine airfoil comprising: a. a base segment having an impact resistant leading edge section proximate to the leading edge comprising a metal or metal alloy having a yield strength of at least about 250 ksi and an elongation percentage of about 12% or less; and b. an erosion resistant coating overlaying the base segment at least in the leading and trailing edge portions of the pressure side, the erosion resistant coating comprising at least one ceramic layer having at least one of the following properties: (1) an erosion value of at least about 200 g. of erodent to cause a thickness loss of about 15–20 microns; (2) an erosion volume loss value (V) of about 1.9 or less as defined by the equation V=H −0.18 ×E 0.75 ×F −1.65 wherein H is hardness, E is elastic modulus and F is fracture toughness; and (3) an F value of at least about 1.5 MPa*m 1/2 , and wherein the at least one ceramic layer comprises a ceramic material selected from the group consisting of tantalum carbide, niobium carbide, titanium carbide, titanium aluminum chromium carbide (TiAlCrC), titanium aluminum chromium nitride (TiAlCrN), titanium aluminum nitride (TiAlN), titanium aluminum carbide (TiAIC), boron carbide (B 4 C), and combinations thereof.