On the Dynamics of Transient Plasmas Generated by Nanosecond Laser Ablation of Several Metals

The dynamics of transient plasma generated by UV ns-laser ablation of selected metals (Co, Cu, Ag, Bi) were investigated by the Langmuir Probe method in angle- and time-resolved modes. Multiple ionic and electronic structures were seen for all plasmas with some corresponding to anions or nanoparticle-dominated structures. The addition of an Ar atmosphere energetically confined the plasma and increased the charge density by several orders of magnitude. For pressure ranges exceeding 0.5 Pa fast ions were generated in the plasma as a result of Ar ionization and acceleration in the double layer defining the front of the plasma plume. Several correlations between the target nature plasma properties were attempted. The individual plasma structure expansion velocity increases with the melting point and decreases with the atomic mass while the corresponding charged particle densities decrease with the melting point, evidencing the relationship between the volatility of the sample and the overall abated mass.

Impact of Laser Texturing on Ni-Based Single Crystal Superalloys

Surface laser texturing is used to ensure mechanical anchoring and strengthen adhesion between the interfaces of bond coatless thermal barrier coating system. To anticipate a possible loss of mechanical properties and to adapt to the perpetual evolutions of chemical compositions of the system, we analyzed the microstructural evolutions of different Ni-based single crystal superalloys, induced during infrared nanosecond laser ablation. Localized asperities composed of a melted, re-solidified matter, with a different microstructure from that of the bulk material, were generated. Regarding asperity morphologies, recrystallization within the latter could be avoided. Then, to compare different Ni-base single crystal superalloys, the thermal-affected volumes were characterized for two patterns textured under different energetic conditions. It seems that all the studied single crystal superalloys behaved quite similarly during nanosecond laser ablation. Finally, according to these results, ablation kinetics between the γ and γ’ phases of Ni-based superalloys could not be homogeneous.