Partial laser and gas nitriding of titanium components

Abstract

Abstract Gas nitriding and laser gas nitriding processes were studied to produce thick and well adhering nitride layers on titanium alloys. A multitude of process parameters have been varied for the nitriding of Ti-6Al-4V substrates. The nitride layers were investigated with optical and electron microscopy, micro hardness testing and glow discharge optical emission spectroscopy. Gas nitriding resulted in strongly adherent nitride layers of up to 5 µm in thickness. Laser gas nitriding with high laser output resulted in very thick (> 500 µm) nitride layers with excellent surface adhesion. A partial melting of the surface during the process altered the surface contour; hence, a reshaping of the component may be necessary. A melting of the substrate surface was avoided through laser gas nitriding with low laser output and additional cooling. However, the up to 100 µm thick nitride layers showed cracks at the interfaces to the substrate.