Effect of thermal treatment on mechanical and tribological properties of hybrid coatings deposited by sol-gel route on stainless steel

This paper deals with the effect of thermal treatment on the mechanical and tribological properties of an organic-inorganic hybrid coating deposited on stainless steel 430. Organic-inorganic coating derived from glycidoxypropyltrimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(OsBu)3 were prepared via sol-gel route and deposited by dip-coating process with various thicknesses. A preliminary thermal analysis (DTA, TGA) of xerogel obtained by hydrolysis and condensation reaction of sols, highlighted three characteristic domains of temperature (110-200. °C, 250-300. °C, 400-500. °C). When thermal treatments were applied to the coated stainless steel in these temperature domains, the tribological behavior (wear and friction) underwent strong changes, analyzed from linear ball/plane tribometry. The tribological tests showed a lower friction coefficient and wear after thermal treatment at a temperature in the domain 250-300. °C. In order to explain this phenomenon, xerogel structure was studied from XRD and Raman spectroscopy and correlated to the mechanical and adhesive properties and to the tribological behavior.