EFFECT OF Hf ON THE INTERFACIAL REACTION BETWEEN A NICKEL BASE SUPERALLOY AND A CERAMIC MATERIAL

The influence of Hf content on the wettability and interfacial reaction between a nickel base superalloy and a ceramic material was investigated by using a sessile drop method. The wetting angle was measured through the geometric parameters of the metal drop. The interfacial morphology and elements distribution were studied by SEM and EPMA, respectively. XPS was employed to study the phase formation at the metal-ceramic interface. The relationship between wettability and interfacial reaction was discussed. It was found that the wetting angle of the metal drop on the ceramic substrate was decreased with increasing Hf content in the alloy and the wettability of the studied superalloy on the ceramic material was enhanced with increasing Hf content in the alloy. When the content of Hf increased from 0.1% to 2.0% (mass fraction), the wetting angle decreased from 132 degrees to 112 degrees. The interfacial reaction led to a sharp decrease in wetting angle as Hf content was 1.5%. The product of interfacial reaction was HfO2 and the thermodynamic analysis indicated that Hf was able to substitute Si in SiO2 in the ceramic material.