Wetting Behaviors of Pure Nickel and Nickel-Based Alloys on Sintered ZrB<sub>2</sub>-SiC Ceramics

Abstract

The wetting and spreading behaviors of pure nickel and nickel based alloys on sintered ZrB2-SiC ceramics and their interfacial microstructures were investigated in this presentation. The nickel-based alloys were mainly the commercial nickel-molybdenum-chromium products. The wetting and spreading properties were observed by a real-time thermal optical measurement system under flowing argon-5%hydrogen atmosphere. As temperature increased, the pure nickel cylinder sample on ZrB2-SiC substrate had few changes before 1228°C except for the thermal expansion in size. After that, liquid phase formed and spread gradually on the ceramic substrate. The contact angle was about 15o after holding 15min at 1600°C. Therefore, pure nickel could contact sintered ZrB2-SiC ceramics well. Meanwhile, the introduction of molybdenum and/or chromium in the pure nickel was beneficial for the wetting of nickel on sintered ZrB2-SiC ceramics. The contact angles of Ni-28Mo and Ni-16Mo-23Cr alloys on sintered ZrB2-SiC ceramics after 1600°C/15min were 13o and 2o, respectively. In addition, the temperatures of the liquid drop formed rose obviously in contrast to the pure nickel. The SEM images indicated that the interfacial microstructures of Ni-based alloys on sintered ZrB2-SiC ceramic substrates were uniform and the dissolved boundaries showed that they had a good bonding. However, some cracks were found in the Ni/ZrB2-SiC system for their high thermal mismatch. On the other hand, the Ni-Mo (-Cr)/ZrB2-SiC interface had few defections and evident elemental diffusion between the ceramic substrates and the alloys were found at the interface.