Structure and properties of hard coatings produced by dynamic ion mixing

A new technique using energetic ion beams has been developped for depositin g advanced coatings resulting in improved properties for tribological and c orrosion protection applications. Hard coatings relatively thick (1 - 2 mu m) have been produced by combining a physical vapor deposition method with simultaneous ion bombardment using a high energy ion beam (100 - 400 KeV) c alled Dynamic ion mixing(DIM). One of the most important features of this t echnique is to produce interface mixing at room temperature which results i n a broad interface of graded composition with excellent adhesion. Differen t types of hard coatings : TiB2, SiC, NiTi(N) have been produced by DIM on different substrates (silicon steel, TA6V) and the influence of the ion mix ing effect on their structure, mechanical, tribological and corrosion prope rties has been studied. The chemical composition and depth profiles have be en determined by RES and SIMS; density measurements are performed by X-Ray reflectometry and the microstructure and phase characterization is obtained by TEM, HRTEM and XRD. Scratch tests have been conducted for controling th e adhesion performance as well as friction and wear experiments with a conv entional pin-on-disk system. For all these coatings the enhancement of crys tallization and densification as well as increased adhesion and wear resist ance improvement were commonly observed features. The influence of SiC coat ings on the corrosion protection of an AISI 321 stainless steel in 1N H2SO4 was also studied by means of cyclic voltametry investigations. It has been observed that the corrosion resistance of SiC coated stainless steel is co nsiderably improved by DIM. The structure modifications and improved proper ties will be discussed in relation with the mixing effects in collision cas cades.