Thermochemical heat treatment of steel substrates using borane-amine adducts as precursors

A novel approach to gas boronising has been carried out to systematically t est organoboranes as precursors for low pressure gas boronising. The precur sors of the group of borane-amine adducts were synthesised and subsequently applied to gas boronising of steel 42CrMo4 (AISI 4140). Characterisation o f the boride layers were performed using glow discharge optical emission sp ectroscopy, X-ray photoelectron spectroscopy, SEM, and metallography. Ultra -microhardness was also determined and the wear behavior was simulated. Wit h the precursors borane-triethylamine adduct and borane-diethylamine adduct gas boronising was possible. Single phased iron boride layers of type Fe2B with a thickness of several micrometres were generated. The carbon, nitrog en, and oxygen contamination of the boride layers was low. The boride layer s are not completely compact which results in a lower hardness compared wit h commercial powder pack boronised samples. The wear behavior is similar to powder pack boronised steels and is significantly better than the untreate d samples. (C) 2001 IoM Communications Ltd.