Fragmentation mechanism and “critical velocity” of ceramic particles during cold spray MMCs – a new modelling framework and experimental validation

Ceramic particles do not have the condition to form metallurgical bonding with matrix metal materials during cold spray. These ceramic particles or their fragments are mainly embedded into the matrix through mechanical interlocking. However, till now, the fundamental deposition mechanism of ceramic particles is still not well understood. Understanding the deposition and fragmentation mechanism of ceramic particles during cold spray process is critical when cold spray is used to fabricate metal matrix composites (MMCs). Therefore, we developed a new modelling approach by coupling “dynamics Weibull distribution” constitutive relation with cohesive elements to simulate the ceramic fragmentation behaviour during cold spray deposition of MMCs. Based on the newly developed model and simulation results, we proposed a new “critical velocity” concept to predict the moment that the ceramic particles fracture upon impact during cold spray. The results indicate that the fragmentation critical velocity increases as the matrix’s hardness reduces, suggesting that ceramic particles are easier to fracture when impacting on hard materials. The modelling results are also well-validated by our well-designed experiments. With this new model, the fragmentation behaviour of ceramic particles during cold spray MMC deposition, including the number and size/spatial distribution of fragments can be well predicted.