Structure and properties of hard coatings produced by dynamic ion mixing

Abstract
A new technique using energetic ion beams has been developped for depositing advanced coatings resulting in improved properties for tribological and corrosion protection applications. Hard coatings relatively thick (1 - 2 µm) have been produced by combining a physical vapor deposition method with simultaneous ion bombardment using a high energy ion beam (100 - 400 KeV) called Dynarnic ion mixing(DIM). One of the most important features of this technique is to produce interface mixing at room temperature which results in a broad interface of graded composition with excellent adhesion. Different types of hard coatings : TB₂, SiC, NiTi(N) have been produced by DIM on different substrates (silicon, steel, TA6V) and the influence of the ion mixing effect on their structure, mechanical, tribological and corrosion properties has been studied. The chemical composition and depth profiles have been determined by RBS and SIMS ; density measurements are performed by X-Ray reflectometry and the microstructure and phase characterization is obîained by TEM, HRTEM and XRD. Scratch tests have been conducted for controling the adhesion performance as well as friction and wear experiments with a conventional pin-on-disk system. For all these coatings the enhancement of crystallization and densification as well as increased adhesion and wear resistance improvement were commonly observed features. The influence of SiC coatings on the corrosion protection of an AISI 321 sîainless 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 considerably improved by DIM. The structure modifications and improved properties will be discussed in relation with the mixing effects in collision cascades.