CHARACTERIZATION AND KINETICS OF PLASMA-PASTE-BORIDED AISI 316 STEEL

In this work, AISI 316 steel was plasma-paste borided in a gas mixture of 70 % H-2-30 % Ar using a mixture of 30 % SiC + 70 % B2O3 as a boron source. The samples were treated at temperatures of (700, 750 and 800) degrees C for (3, 5 and 7) h. The morphology of the formed boride layers was examined by light microscope and scanning electron microscope coupled to an EDS analyser. The borides present in the boride layer were identified by means of XRD analysis. The boron-activation energy for the AISI 316 steel was found to be equal to 250.8 kJ mol(-1). This value for the energy was compared to the literature data. A regression model based on a full factorial design was used to estimate the boride layers' thicknesses as a function of the boriding parameters: time and temperature. A comparison was made between the values of the boride layers' thicknesses estimated from the regression model with those given by an empirical relation. In addition, an iso-thickness diagram was plotted to predict the boride-layer thickness as a function of the processing parameters. This iso-thickness diagram can serve as a simple tool to select the optimum values for the boride layers' thicknesses for a practical utilisation in industry for this kind of steel.