Interaction between Two Ni-Base Alloys and Oxide Ceramics: SiO_2, ZrO_2; HfO_2; Al_2O_3

摘要

To better understand the problem of corrosion of oxides by molten superalloys, sessile drop experiments were conducted under vacuum in a Mo-resistor furnace, followed by interfacial characterizations (SEM, EDS analyses, X-ray diffraction). The behavior of two Ni-base alloys A and B are compared on the basis of their contact angles on four different oxide ceramics: amorphous silica, MgO stabilized zirconia, hafnium oxide and alumina. Alloys A and B have a similar composition, but only A contains Hf (1.3 weight percent). The alloy with Hf forms a HfO_2 layer at the metal / ceramic interface, whereas the alloy without Hf develops an Al_2O_3 layer at the interface. Despite this difference, their contact angles on the four studied ceramics are quite similar. The results allow us to distinguish two kinds of wetting behavior on the four ceramics: on HfO_2 and Al_2O_3 the angles are wetting and stable, while on SiO_2 and ZrO_2 they decrease with time from a non-wetting value, never reaching an equilibrium angle during a one hour dwell.