The cold spray deposition mechanism of Ultra-High Molecular Weight Polyethylene (UHMWPE) requires a detailed understanding of strain rate sensitivity of UHMWPE. The yield and flow in UHMWPE are complex and sophisticated compared to metals due to their dependency on time, temperature, strain, strain-rate and the history of the processing. In this research work, powder-sintered UHMWPE of 10.5 Mg/mol was subjected to various strain-rates ranging from 10-2 s-1 to 103 s-1 via low compression strain-rate testing and Split Hopkinson Pressure Bar testing (SHPB). The experimental true stress-strain curves in compression of a sintered UHMWPE at pre-yield, yield point, and post-yield were analyzed. The pre-yield and yield point region, 10.5 Mg/mol UHMWPE exhibited an increase in the tangent modulus and the yield stress with an increase in strain rate. Further, the post-yield phenomenon in UHMWPE shows no apparent post-yield softening and shows an increase in the strain hardening with an increase in the strain-rate. The curves at increasingly higher strain rates showed an increasingly pronounced bi-linearity to its flow behavior with the rate of hardening increasing above 10~15% strain. Under the domain tested, the strain rate dependence for UHMWPE can be depicted by a logarithmic fit.

The cold spray deposition of ultra high molecular weight polyethylene (UHMWPE) powder mixed with nano alumina, fumed nano alumina and fumed nano silica was attempted on two different substrates namely polypropylene (PP) and aluminum (Al). Approximately 4mm and 1mm thick coating were observed on Al and PP substrates respectively with UHMWPE and fumed nano alumina mixture. The nano ceramic particles played an important role as a bridge bond between the particles. The coatings with nano alumina, fumed nano alumina and fumed nano silica were very contrasting in terms of coating thickness. Gas temperature and pressure played an important role in the deposition. The differential scanning calorimetry (DSC) results of the coatings showed that UHMWPE was melt crystallized after the coating. The substrate properties also affected the deposition mechanism greatly.