Surface morphology of a laser surface nitrided and etched Ti-6Al-4V alloy

A laser surface nitriding process was applied to a Ti-6Al-4V alloy to obtain a surface layer consisting of TiN dendrites and a titanium alloy matrix. The dendritic volume fraction can be controlled by varying the nitrogen flow rate during the laser gas nitriding. By subsequently applying a selective etching process, the matrix material in the alloyed layer can be selectively removed and a three-dimensional network of TiN dendrites is left on the surface anchoring on the substrate. The 3D dendritic network provides extra surface area and a locking mechanism for the adhesion joint with a ceramic layer. The interface cross-section microstructure of such adhesion jointing surfaces is discussed.