Oxide Spallation during Post-Isothermal High Temperature Oxidation Cooling of Cr-rich Cast Alloys highly alloyed with Hf
Cobalt, nickel and iron-based alloys containing 25wt.%Cr and strengthened either by chromium carbides or by HfC were oxidized at 1000, 1100 and 1200°C to obtain external oxide scales. The spallation of these oxides during the post-oxidation cooling was studied by exploiting the cooling part of the thermogravimetry curves. The best resistant alloys against scale spallation were the iron-based alloys which did not lose oxide. The nickel-based alloys well behaved too. The worst alloys were the cobalt alloys, principally due to the complex composition of the oxide scales. Beside the base element, the thickness of the oxide was also identified as a major parameter. The presence of Hf with contents much higher than usual was also beneficial for the resistance against spallation.
Superalloys: a technical guide
Superalloys: a technical guide , Superalloys: a technical guide , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
Experimental and thermodynamic study of the high temperature microstructure of tantalum containing nickel-based alloys
Abstract Experiments and thermodynamic calculations were performed on three nickel-based alloys containing chromium, carbon and tantalum. Solidus and liquidus temperatures, and natures and surface fractions of the carbides after exposure for 100 h at 1000, 1100 and 1200 ∘C were determined for each alloy. These results are compared with calculated results, using a thermodynamic database. Good agreement was generally found for the solidus temperatures but less good agreement for the liquidus ones. For alloys containing chromium carbides alone, carbide fractions and matrix compositions correspond to calculation results. But the presence of tantalum carbides in the third alloy was not predicted by calculations.