Cavitation erosion of laser l11eltedand laser nitrided Ti–6Al–4V

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Abstract
The effect of laser surface treatment on the cavitation erosion resistance of Ti–6AI–4 V is reported. Surface melting and alloying of the alloy is undertaken in a controlled atmosphere of argon, or alternatively, nitrogen diluted with argon, using a continuous wave CO2 laser. The gas composition of the atmosphere is variable, set at either 100%Ar, 90%Ar + 10%N2, or 80%Ar + 20%N2, by volume. The microstructure of the laser processed layer is martensitic when processed in pure argon and exhibits a continuous surface layer of TiN when processed in a nitrogen containing atmosphere. All material melted in an atmosphere containing nitrogen exhibits some cracking in the processed layer. The results presented demonstrate that the steady state erosion rate is significantly decreased when the material is processed in a nitrogen containing atmosphere. The enhanced erosion resistance is attributed to the nitrogen alloyed laser processed α titanium microstructure, not the continuous TiN surface layer. MST/3073