!Insights into arc-assisted self-propagating high temperature synthesis of TiB2-TiC ceramic coating via wire-arc deposition

TiB2-TiC ceramic coating was fabricated by wire-arc deposition of Ti-B4C cored wire in conjunction with self-propagating high temperature synthesis (SHS) technology, to enhance the hardness and wear resistance of Ti. Results showed that a periodic combustion reaction, triggered by the capillary infiltration of molten Ti sheath into the inside B4C particles, occurred as the wire entered the arc zone. During combustion reaction, B4C experienced the course of dissolution as well as the transformation of decarbonization expressed as B4C -> B13C2 -> B13Cx(1.27 < x < 2.00). In particular, the loss of C was more notable at combustion front region. The as-synthesized coating exhibited ultralow porosity thanks to the elevated adiabatic temperature, and possessed gradient microstructures formed due to the dissolution-precipitation mechanism. Mechanical and tribological tests showed that the coating had ultrahigh microhardness (2140 HV0.5, close to theorical value) and low wear rate (5.5 x 10(-3) mm(-3) min(-1)-N-1). The superior performance was attributed to ultralow porosity and high-strength coherent TiB2/TiC interface.