Diffusion Layers with Ti and Ti+Al Formed on 316L Austenitic Steel by a Pack Cementation Procedure

Abstract

Pack cementation procedure implies the use of a powder mixture containing the diffusive elements, which in our case are either Ti or Ti+Al, Al2O3 and NHCl as activator. In the case of titanizing the powder mixture contained 77% in weight Ti, while for alumino-titanizing Al/Ti = 1/5 ratio was employed. NH4Cl content was 3% in weight in all cases. Aluminium additions to the powder mixtures led to a decrease of the process temperature. Activation energy for the aluminizing of austenitic 316L steel is 73.87 KJ/mol, much smaller than for the titanizing, 257.86 KJ/mol. Activation energy for alumino-titanizing, in the same conditions, is 146.01 KJ/mol. All diffusion coatings, in the Ti – 316L and Ti+Al – 316L couples are formed of two layers having different structures and compositions. All couples were investigated by optical microscopy, electron microscopy (SEM and EDX), X-ray diffraction and microhardness trials.

Biovitroceramic Coatings on Modified Surface of 316L Austenitic Stainless Steel

“…Prior to obtaining the enamelled layers, samples were thermochemically treated by titanizing by pack cementation procedure. The pack cementation procedure with obtaining of Ti diffusion coatings was described in detail elsewhere [22][23][24]. This procedure consists in packing 316L austenitic stainless steel samples in a powder mixture.…”