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Surface modification by solid phase titanium diffusion of a 316L austenitic steel

M. BRITCHI1,* , N. ENE1, M. OLTEANU1, C. RADOVICI1

Affiliation

  1. Romanian Academy, Institute of Physical Chemistry “Ilie Murgulescu” ICECHIM Splaiul Independentei 202, sector 6, Bucharest, ROMANIA

Abstract

Surface modification of austenitic steels with high Cr and Ni contents was performed in order to obtain titanium-containing diffusion layers. The steel we employed was 316L type used in implantology with a composition: C=0.03; Cr=16-18; Ni=10-14; Mo=2-3; Mn=2.0; Si=0.75; P=0.045; S=0.03 and N=0.10, in % weight. The diffusion layers were prepared following a thermo-chemical treatment that implied a powder packing procedure. The packing mixture was made of titanium powder of different proportions, aluminium oxide and ammonium chloride of concentration up to 3 % in weight. Working temperature and time were varied. Solid phase diffusion layers need high temperature, over 900ºC and long time period, many hours. The main advantage of titanizing by powder packing procedure is that the layer is an alloy type and is very uniform no matter the shape and the roughness. Diffusion layers obtained under different temperature and treatment duration conditions were investigated on their cross sections by optical microscopy and Vickers microhardness trials. The nature of the different phases formed in the diffusion coatings were investigated by X-ray diffraction. By surface modification of the metallic parts made of 316L austenitic steel, we followed two objectives: (i) to increase the corrosion resistance, knowing the fact that implants manufactured from such steel present a certain degree of leaching which leads to expelling extremely toxic chromium ions into the organism and (ii) to prepare the surface such as to be proper for the covering with biovitroceramic coatings..

Keywords

Titanium diffusion coatings, 316L austenitic steel.

Submitted at: Dec. 17, 2007
Accepted at: July 10, 2008

Citation

M. BRITCHI, N. ENE, M. OLTEANU, C. RADOVICI, Surface modification by solid phase titanium diffusion of a 316L austenitic steel, Journal of Optoelectronics and Advanced Materials Vol. 10, Iss. 8, pp. 2159-2162 (2008)