The Role of Target Melting in Particle Impact Ignition with Inert Particulate

Abstract

The high gas temperatures and oxygen pressures in the turbine of oxygen-rich turbomachinery put conventional engineering alloys such as IN718 at risk of particle impact ignition, i.e., metal fires initiated when particulate strikes a solid surface. The standard model of particle impact ignition assumes that the impacting particle must first ignite in order to kindle to the target material. Here, we invalidate this belief through particle impact ignition experiments which show that IN718 can ignite when struck by inert Al2O3 particles with supersonic impact velocities. Through post-mortem analysis of non-ignited samples, we find that subsonic particle impact causes minimal crater damage whereas supersonic particle impact leaves extensive crater plasticity and pileup, with evidence of molten ejecta near the impact site. Complementary finite element simulations of supersonic impact events confirm extreme adiabatic heating and localized melting. These findings demonstrate that particle impact can drive target ignition even in the absence of particle burning provided the thermal excursion at impact exceeds the melting point of the target material.