Melting and Ejecta Produced by High Velocity Microparticle Impacts of Steel on Tin

Abstract

At sufficiently high velocities, a microparticle impacting a metal substrate can cause ejection of material from the substrate and impact-induced melting, both of which can result in erosion. Here we directly image the impact of individual hard steel microparticles on soft tin substrates, at controlled impact velocities in the range of ~100 to 1000 m/s. Using scanning electron and laser-scanning confocal microscopy, we characterize the surface morphology, depth, and volume of each impact crater. We observe a gradual onset of impact-induced melting in the craters, as well as the production of increasing amounts of ejecta from the target metal. By comparing measurements of impact and rebound velocity to an elastic-plastic model, we observe that at a high enough impact velocity, melting and ejection begin to consume additional kinetic energy beyond that expected by plastic deformation of the target material alone. By calculating the excess energy dissipation using this elastic-plastic model, we show that although this divergent behavior is associated with the onset of melting, the majority of the ejected volume must be solid rather than liquid.

Does speed kill or make friction better? — Designing materials for high velocity sliding

“…Our transition velocities marking the onset of melting are in astonishing agreement with recent experimental studies of microparticles impacting on a range of metallic surfaces at ballistic velocities [72,73,27]. They find that the ratio of particle rebound velocity to impact velocity scales with speed according to a power law up to impact velocities of 400-600 m/s, but then it starts deviating considerably.…”

“…They find that the ratio of particle rebound velocity to impact velocity scales with speed according to a power law up to impact velocities of 400-600 m/s, but then it starts deviating considerably. This deviation marks the transition to a different physical regime, and it can be quantified as an excess energy that is available for other mechanisms to occur, in particular local melting of the substrate due to adiabatic heating [27]. A comparison of the small melted volumes with their large lateral extent suggests very thin melted and resolidified layers of substrate material, which compares excellently with our own findings.…”

“…At the other extreme, supersonic projectiles [16], permanent magnet drives for turbochargers [25], and processes associated with technologies such as explosive welding [26,15] result in interface velocities of 1 000 m/s and beyond. These velocities and the associated high shear rates are often accompanied by significant frictional heating, leading to a decrease in the resistance to shear induced by surface melting [27]. The access to experimental data for materials sliding at extreme velocities requires the use of specialized laboratory equipment.…”

Recent advances on bonding mechanism in cold spray process: A review of single-particle impact methods

“…[ 107 ], copyright 2020 Elsevier; (a, e and d, h) co-deformation, (b, f) penetration, and (c, g) splatting; (i) impact modes predictive map for similar and dissimilar pure metals (square and circular data points), and now showing its accurate prediction of impact mode for alloys (starred data points from Refs. [ 108 , 109 ]), reprinted with permission from Ref. [ 107 ], copyright 2020 Elsevier; and (j) conceived connection between bonding types, impact cases (particle/substrate configurations), and impact modes.…”

“…copyright 2020 Elsevier, f, g, reprinted with permission from Ref [107],. copyright 2020 Elsevier; (a, e and d, h) co-deformation, (b, f ) penetration, and (c, g) splatting; (i) impact modes predictive map for similar and dissimilar pure metals (square and circular data points), and now showing its accurate prediction of impact mode for alloys (starred data points from Refs [108,109][107],.…”