Interfacial Reaction between Iron‐Based Alloys and Polycrystalline α‐Al 2 O 3

The effect of temperature, atmosphere, and elemental concentrations of boron and phosphorous in ferrous alloys on the wettability of polycrystalline α‐Al 2 O 3 was studied. The investigation of the wetting behavior is of major importance to the infiltration of steel into open foam ceramics. In reference Fe‐0.46 wt% C iron samples, the contact angle was investigated between 1550 and 1650 °C under Ar‐H 2 and Ar atmospheres and was found to decrease with increasing temperature and increasing oxygen partial pressure. Furthermore, no FeAl 2 O 4 (hercynite) spinel type inclusions were found in Fe/Al 2 O 3 experiments. In the Fe‐P binary alloys, θ decreased with increasing phosphorous content and was ≈112° for the Fe‐0.299 wt% P alloy at 1600 °C. For the Fe‐B binary alloys, a strong influence of boron on the contact angle was found. Secondary neutral mass spectrometry (SNMS) analysis showed a maximum in the boron concentration in the first 50 nm of the metallic side of the interface. In the FeCrMnNi‐P high‐alloys specimens, a reaction layer was found between the steel/ceramic interfaces. The contact angle was ca. 90°, lower than the Fe‐P binary alloys.