Microstructure and wear assessment of TIG surface alloying of CP-titanium with silicon

Tungsten Inert Gas (TIG) process has been employed to produce surface alloyed tracks on preplaced CP-Ti substrate with Si to improve wear resistance. Uniform alloyed tracks with hypo eutectic binary Ti–Si compositions have been achieved using preplaced layers with Si amounts of up to 40 at.%. Si content of the TIG alloyed tracks was found to be affected by the TIG heat input and Si amount of the preplaced layer. The microstructures of the surface alloyed tracks showed phases of primary α-Ti in dendrites and eutectic lamellas of α-Ti and Ti₅Si₃ within the interdendritic regions using optical and scanning electron microscopy, X-ray diffractometry, and energy dispersive spectroscopy. Finer dendrites were found at lower heat input. A maximum micro hardness value of 750 HV was found in the surface alloyed track, which is ~4 to 5 times of that of the substrate material (180 HV). Pin-on-disk wear tests exhibited the better performance of the surface alloyed tracks than the untreated material which is attributed to the presence of Ti₅Si₃ intermetallic compound in the microstructure.