Jetting-Out Phenomenon Associated with Bonding of Warm-Sprayed Titanium Particles onto Steel Substrate

Abstract

Titanium powder particles accelerated and simultaneously heated by the supersonic gas flow were deposited onto steel substrate by the warm spraying process. The sprayed particles were heavily deformed and bonded to the substrate in solid state. Especially, all the deposited particles showed jetting-out of materials out of the particle-substrate interface triggered by the adiabatic shear instability known to occur under such shock impact conditions. High-magnified images showed that grain refinement occurred in the jetting-out region by dynamic recrystallization. Furthermore, the elemental analysis using the electron energy loss spectrum showed jetting-outs of the substrate as well as the particle. Numerical simulation based on the Johnson-Cook plastic deformation model showed that the jetting-out phenomenon commences about 10 ns after the initial contact of the particle with the substrate and at a position away from the center bottom of particle, where the highest compressive stress is experienced.