AN EXPERIMENTAL-STUDY OF THE REMELTING OF AN FE-C-CR-SI-B OVERLAY WITH A MICROBEAM PLASMA-ARC

An Fe-C-Cr-Si-B overlay produced by a plasma transferred are process o n 1045 steel was remelted by multipass or single-pass scanning with a plasma are of 2 or 4A, and the effects of remelting on microstructure and wear performances were characterized. We show that non-dendritic, equiaxed microcrystallines and refined dendritic structure were presen ted cyclically from the remelting region/substrate interface to the to p surface. In the remelted regions, the shrinkage holes were reduced i n size and the microstructure was greatly improved. An amorphous struc ture was also found in some areas by transmission electron microscopy (TEM). After remelting, the main constituent phase in the untreated ov erlay (i.e. ferrite) converted to austenite, while the intermetallic c ompounds (Fe,Cr)(7)C-3 and FeB decreased in content and dispersed into the matrix as extremely fine particles. Remelting also improved the h ardness and wear resistance of the iron-based overlay. However, these effects were not very significant. (C) 1998 Elsevier Science S.A.