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 and 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 deposition FeCl3 and Fe(CO)(5) were used as precursors. A boriding depth of several micrometres was achieved, in which the microhardness amounts to 1500-2000 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 controlled by the process pressure. Microhardness values above 2000 HV0.02 are achieved at low carbon content in the layers. In order to deposit well-adherent Fe2B layers on borided substrates intermediate FeB layers or inclusions have to be avoided. (C) 1999 Elsevier Science S.A. All rights reserved.