Solar gas nitriding of Ti6Al4V alloy

The main purpose of this work was to study the activating effect of concentrated solar energy (CSE) on the high-temperature nitriding of Ti6Al4V alloy. Solar nitriding was conducted using a low-cost solar installation based on a Fresnel lens with a maximum density power of 250 W/cm2 at its focus. Prior to the solar nitriding study, Ti6Al4V was submitted to high-temperature thermochemical treatments using an electrical furnace in a conventional manner. A comparison between the two processes considering the effect of nitriding time and temperature on the hardness, thickness and composition of the nitrided layer is presented. Characterisation of the treated samples by optical and SEM microscopy, microhardness measurements and XRD analysis reveals an important reduction in the nitriding time when concentrated solar energy is used versus the traditional method. The maximum hardness of the solar nitrided samples (2100 HV) was achieved after treatment at 1200 °C for 15 min. This value is similar to that obtained when samples were heated at the same temperature in the electrical furnace for 8 h.