Origins of a Low-Sulfur Superalloy Al2O3 Scale Adhesion Map

Low-sulfur single-crystal Ni-base superalloys have demonstrated excellent cyclic oxidation resistance due to improved Al2O3 scale adhesion. This derives from preventing deleterious interfacial sulfur segregation that occurs at common ppm levels of S impurity. Multiple hydrogen-annealing desulfurization treatments were employed produce a continuum demonstrating this oxidative transition, using 1 h 1100 °C for 500 1000 h. The content was determined by glow discharge mass spectrometry. complete gravimetric database 25 samples is revealed and correlated with content. Maximum adhesion (i.e., no weight loss) achieved ? 0.3 ppmw S, significant spallation (20–30 mg/cm2) above 2 ppmw, transitional behavior between S. A map suggested enabled when the total reservoir less than one atom per Ni interface atom. Equilibrium models further suggest may be minimized (~1% 0.2 bulk), regardless section thickness. 1st order effects thus been PWA 1480 having Y, Zr, or Hf reactive element dopants possibility confounding effects. results are compared 2nd generation 1484, Rene’N5, N6, CMSX-4® SLS, all dopants.