Abstract
Cast steel was locally hard-faced using inserted hard alloy powder layer containing several percent of spray alloy (BNi 3). The vertical cross-section of the inserted layer was examined regarding microstructure with EPMA and hardness with a Vickers hardness tester. The results obtained are as follows: Sound inserted layers of 3 mm in thickness were confirmed to be formed without any defects at the surface of cast steel. An intermediate layer with some lump shaped particles were formed at a region between the inserted layer and mother metal (cast steel). The lump shaped particles were identified to be Fe3W3C. The hardness of cast steel was about HV 300, while the inserted layer exhibited a hardness of HV 600 to 1400. The maximum hardness was obtained in the case of hard alloy powder containing 20 vol.% spray alloy. This was considered due to the formation of a hard martensitic structure at the bonding phase in the hard alloy powder. No effects of post heat treatment on the hardness distribution in the inserted layer were detected. The present method using the inserted hard alloy powder is therefore considered to be very effective for the locally hard facing of cast steel.
