イオン交換膜-複数陽極システムを用いたFe-W合金めっきの耐熱特性および耐溶融亜鉛侵食性

Abstract

We have investigated the heat resistance properties of Fe-W alloy films electroplated using an ion exchange membranes - multiple anodes systems. The room temperature hardness of Fe-W alloy film increased with increasing heat treatment temperature and reached HV1200 after the heat treatment at 700°C. While the film was amorphous in the as-plated state, it was partially crystallized by heat treatment at over 600°C, indicating that the increase in the hardness was caused by mechanism of precipitation hardening. The high hardness of the Fe-W film was maintained even when the hardness was measured at high temperatures. Wear resistance of Fe-W alloy film was lower than those of electroplated Ni-W alloy and Cr films in the as-plated states. However, the wear resistance of Fe-W alloy increased and surpassed the values of the Ni-W alloy and Cr films after heat treatment. Fe-W alloy film with a higher W content showed higher resistance to the erosion by molten zinc. No erosion by molten zinc was observed for the Fe-W alloy films containing W more than 35 wt%. The Fe-W alloy film was found to form layered oxide phases on its surface. The oxide layer formed on the surfaces of the Fe-W film, including the inner surface of the cracks in the film, seemed to work effectively as a barrier to the molten zinc erosion.