Characterization and kinetics modelling for the titanium silicide layer formed on the Ti6Al4V alloy by pack siliconizing

The present study reports on silicide coating on Ti6Al4 V alloy by pack siliconizing technique. This siliconizing surface process was carried out in medium consisting of mixture of silicon, alumina, and ammonium chloride at 1000, 1100, and 1200 degrees C for 2, 4, 6, and 10 h in an argon atmosphere. The presences of outer TiSi2 and the inner TiSi and Ti5Si3 silicide compounds were verified by X-ray anlaysis technique and scanning electron microscope (SEM) equipped with an energy dispersive spectroscope. Depending on process time and temperature, the layer thickness of silicides formed on the surface of substrate materials changes between 9 and 47 mu m leading to a diffusion controlled process. The hardness of silicides compounds measured by means of Vickers indenter ranged from 940 to 1647 HV. For silicon diffusion in the silicide compounds an activation energy of 216.27 kJ mol-1 was determined using the integral method. TG-DTA results revealed that silicide coating is stable up to 850 degrees C.