GAS-PHASE REACTIONS DURING SIMULTANEOUS BORONIZING AND ALUMINIZING OF STEELS

The surface reactions proceeding at the substrate-gas interface during the simultaneous boronizing and aluminizing of steels were investigated. The gas phase transport of Al and B was determined for their subhalides obtained from B4C-Al-NaF powder mixtures. The equilibrium composition of the gas mixture during aluminizing and simultaneous boronizing and aluminizing was calculated using a system of equations for the isotherm of the chemical reactions. It was shown that simultaneous boronizing and aluminizing in the gas phase could be achieved within the narrow temperature range 850-900-degrees-C irrespective of the BF3 to AlF3 ratio. The theoretical results were confirmed experimentally during the simultaneous boronizing and aluminizing of steel alloys.