MICROSTRUCTURE OF Fe-Cr-C HARDFACING ALLOYS WITH ADDITIONS OF Nb, Ti AND, B.

The abrasive wear of machine parts and tools used in the mining, earth moving, and transporting of mineral materials can be lowered by filler wire welding of hardfacing alloys. In this paper, the microstructures of Fe-Cr-C and Fe-Cr-C-Nb/Ti hardfacing alloys and deposits and those of newly developed Fe-Cr-C-B and Fe-Ti-Cr-C-B ones are described. They show up to 85 vol. % of primarily solidified coarse hard phases; i. e. , carbides of MC-, M//7C//3-, M//3C-type and borides of MB//2-, M//3B//2-, M//2B-, M//3B-, M//2//3B//6-type, which are embedded in a hard eutectic. This itself consists of eutectic hard phases and a martensitic or austenitic metal matrix. The newly developed Fe-Cr-C-B alloys reach hardness values of up to 1200 HV and are harder than all purchased ones. The primary solidification of the MB//2-type phase of titanium requires such high amounts of titanium and boron that these alloys are not practical for manufacture as commercial filler wires.