The surface of specimens made of 316L austenitic steel was modified by titanium diffusion. The diffusion coatings were obtained by packing in a powder mixture consisting of titanium powder, NH4Cl and Al2O3 powder. The procedure required high temperatures, over 900 °C, and long durations. Atomic titanium was formed in the muffle during the process. Titanium atoms from the metallic part surfaces diffuse towards the interior and a diffusion layer is formed as a function of the steel composition. Titanium diffusion into the surface of 316L austenitic steel determines the formation of a complex coating: a thin layer of TiN at the exterior and a layer consisting of compounds containing Ti, Ni and Fe in the interior of the coating. The obtained coatings were continuous, adherent and had a hardness higher than that of the substrate material. The diffusion coatings were investigated by optical and electron microscopy, X-ray diffraction and Vickers microhardness tests.