Metal molds and machine parts for die-casting need excellent corrosion resistance against molten metals. In this study, we investigated corrosion resistance of various kinds of boride base hard materials ( Mo₂FeB₂-Fe, Mo₂NiB₂-Ni, WCoB-Co, W-Mo₂NiB₂-TiB₂ base cermets and TiB₂ ceramic ) against a molten Al alloy (JIS ADC10), a Zn alloy (JIS D-2) and soft solders (JIS H5A and H70A). The corrosion resistances of these materials were estimated by measuring the dimensional changes after dipping in the molten metals.
The results indicated that the boride base hard materials, especially TiB₂ containing materials had higher corrosion resistance than. conventional materials, such as WC-20mass%Co, SKD61 and SK1151. SEM micrographs showed that the binder phases comprising Fe, Co and Ni in the boride base hard materials react with the molten metals, prior to the boride phase. The boride base hard materials are consequently promising candidates for the die-casting machine parts and molds.