2022-01-07 Innovative and efficient coating development for magnesium components

Aluminum intermetalide coatings on magnesium alloys can be used mainly as interlayers in composite coatings to improve corrosion resistance.

Aluminum intermetalide coatings can be applied by various methods - from powders, alloys, etc. With these methods, coatings are mainly produced from pure aluminum. Vaccines obtained by vacuum methods, in particular (PVD), are more suitable for obtaining multicomponent coatings.

PVD technology allows you to effectively control the properties of the products to be coated, obtaining both single-layer and multi-layer coatings.

At elevated temperatures of 300-400°C, aluminide coatings are subject to absorption, which significantly affects their properties, as absorption leads to the formation of diffusion (mainly intermetallic) layers, which increase the adhesion of the coatings. Additional alloying elements affect both the absorption rate of the precipitated layers and the final properties of the coatings. This effect is even more effective when several layers of different chemical composition are applied. As a result, it is possible to obtain combined coatings in which each layer (diffusion, modified applied) fulfills its specific function.

Changes in the chemical composition of multi-component PVD coatings during heat treatment were investigated during this phase of the project.

All coatings were obtained using an upgraded NNV-6.6-I1 vacuum ion-plasma setup. During PVD application, electric arc sources for titanium and niobium application and a magnetron sputter for aluminum and silicon application were used simultaneously. Precipitation of pure metals was performed under argon at 7x10-4-1x10-3 mm Hg. The nitride coating was applied under an argon atmosphere at a pressure of 3x10-3 with the addition of nitrogen at a partial pressure of 2x10-3 mm Hg.

Figure 1. Appearance of samples 173,176,177,179 (a) before heat treatment and (b) after heat treatment at 330 ° C.

The changes of the most important parameters of the chemical composition - magnesium content in the coating and Mg / Al ratio% from the thawing time are shown in Fig. 2. And the morphology of the surface microstructure is shown in Fig3.

Figure 2. Mg / Al ratios for different samples

Fig 3 sample 173 changes in surface morphology during heat treatment.