Microstructure of TIG Melted Composite Coating on Steel Produced Using 1.0 and 1.5 mg/mm2 TiC at an Energy Input of 2640 J/mm

Abstract

Surface modification by reinforcing ceramic particulates can give protection against wear and corrosion of metal. In this work, two different amounts of TiC powder of nominal size 45 to 100 µm were embedded on AISI 4340 steel surfaces by melting under a Tungsten Inert Gas (TIG) welding torch with an energy input of 2640 J/mm. The microstructure, geometry and hardness of the single track composite layers were investigated. The resolidified melt tracks were hemispherical in shape. With increasing TiC content, the melt dimensions reduced a little but the microstructure had a remarkable change. The track with 1.5 mg/mm2 TiC gave more un-melted TiC, partially melted TiC and agglomeration of ceramic particulates while the 1.0 mg/mm2 track dissolved most TiC particulates and precipitated carbides in the form of dendrite, globular and flower type particles; dendrites are almost absent in the 1.5 mg/mm2 track. A reduced TiC addition created more fluid melt which accelerated dissolution of TiC and that caused more carbide precipitation in the 1.0 mg/mm2 track compared to that with 1.5 mg/mm2 track. The 1.0 mg/mm2 track produced lower hardness of 1065 Hv compared to 1350 Hv for the 1.5 mg/mm2 track.