Formation of iron boride layers on steel by d.c.-plasma boriding and deposition processes

Boriding and deposition of iron borides on Armco iron and the steels Ck45 a nd 42CrMo4 have been investigated at temperatures below 833 K using BCl3-H- 2-Ar gas mixtures activated by pulsed d.c. glow discharges. For the layer d eposition FeCl3 and Fe(CO)(5) were used as precursors. A boriding depth of several micrometres was achieved, in which the microhardness amounts to 150 0-2000 HV0.02. FeB and Fe2B layers could only be obtained with Fe(CO)(5) as iron precursor. The incorporation of carbon in the layers can be controlle d by the process pressure. Microhardness values above 2000 HV0.02 are achie ved at low carbon content in the layers. In order to deposit well-adherent Fe2B layers on borided substrates intermediate FeB layers or inclusions hav e to be avoided. (C) 1999 Elsevier Science S.A. All rights reserved.