High-Temperature Oxidation Resistance of Al₂O₃- and Cr₂O₃-Forming Heat-Resisting Alloys with Noble Metals and Rare Earths

Abstract

High-temperature oxidation behavior of Al 2 O 3 -and Cr 2 O 3 -forming heat-resisting alloys with noble metals (Pd, Pt) and rare earths (Y, Lu) was studied in oxidizing atmospheres (oxygen, oxygen-water vapor) for 18ks at 1473, 1573 and 1673K, by mass gain measurements, amount of spalled oxide, observation of surface appearance, XRD, SEM, EPMA, and TEM. For Al 2 O 3 -forming alloys, noble metal additions did not decrease mass gain, however, increased oxide adherence in both oxidation conditions. On the other hand, yttrium addition decreased mass gain in both oxidation conditions. After oxidation at 1673K, water vapor caused alumina scale spallation, however, 0.5mass% platinum addition showed good oxide adherence. For Cr 2 O 3 -forming alloy, rare earth or silicon addition decreased mass gain, and both rare earth and silicon addition markedly decreased mass gain after oxidation in oxygen for 18ks at 1473 and 1573K. Oxide spallation was amplified by the addition of silicon.

Intergranular Oxidation of Additively Manufactured Ni-Base Alloy 625: The Role of Si

“…5), Si may have also an additional detrimental effect on the performance of a chromia-forming alloy promoting enhanced oxide spallation [69,74,75,77]. The adhesion of Cr 2 O 3 deteriorates with increasing Si content above a certain level due to volume change of SiO 2 on cooling [78] or blocking influx of vacancies resulting in micro-cavities [74]. Nevertheless, the overall effect of moderate alloying with Si is rather positive and is widely practiced in the metallurgy of high-temperature alloys.…”