The metallurgical behavior of B4C in the iron-based surfacing alloy during plasma transferred-arc (PTA) Fe-B4C composite powder surfacing was investigated and discussed in this paper. Based on the experiment results it is found that Fe-B4C composite coatings can only be prepared by PTA powder surfacing in the case that the employed surfacing current is little enough. The metallurgical reactions between Fe and B4C are limited in a very narrow region at their contacting interface in this case. With the increasing of employed surfacing current more and more B4C particles will be fully melted and reacted with the liquid iron-based alloys. However, the products of the metallurgical reactions between them are various for the different powder compositions and surfacing conditions. Most of the B4C particles will be fully melted during the PTA powder surfacing while 200 A or greater surfacing current is used. Furthermore, most of the C element in B4C particles is tending to be graphite rather than reacting with Fe to be carbides during the processing under the Fe-B4C composite powder PTA surfacing conditions. (c) 2005 Elsevier B.V. All rights reserved.