Corrosion-resistant composite titanium nitride layers produced on the AZ91D magnesium alloy by a hybrid method

Composite titanium nitride layers produced on the AZ91D magnesium alloy by a hybrid method including hydrothermal modification of the layer

“…Before the deposition of each of the subsequent coatings, oxides were removed from surfaces by cathode sputtering. The final stage of the hybrid treatment consisted of sealing the layers by a hydrothermal type treatment performed in boiling water bath [8]. The detailed parameters of each of the PVD processes were given in an earlier paper [8].…”

“…3). Nevertheless, the craters, which constitute discontinuities in the outside titanium nitride coating reaching the titanium sub-layer [8], may provide a path through which corrosive environment may penetrate to the AZ91D alloy substrate trough the TiN2Ti1Al10 composite layer, with negative impact on its anti-corrosion properties. The same certainly concerns any other discontinuities which may occur in the layer as shown in Fig.…”

“…The key procedure intended to eliminate the detrimental effect of the unavoidable structural defects and the porosity, specific for the layer produced in PVD processes is a final sealing treatment [8]. The surface of the TiN2Ti1Al10 composite is subjected to hydrothermal sealing at the fourth stage of the hybrid process ( Fig.…”

“…Another highly efficient solution which allows overcoming the problem of low corrosion resistance of the PVD nitride coatings, related to their porosity, has recently been developed in course of our previous investigations [8]. The solution was based on the concept of final chemical type sealing of the composite TiN-Ti-Al type titanium nitride layer with a sub-layer of titanium and aluminium produced on AZ91D magnesium in hybrid process.…”

“…1300 mV). The key solution which allows obtaining such high corrosion resistance increase is the simple but effective process of sealing the layer by hydrothermal treatment in boiling water bath [8]. This solution, proved in commercial anodising of light alloys but never applied in the past to PVD nitrides coatings, is intended to seal the pores and defects in the coating with the products of a chemical reaction induced by the hydrothermal treatment.…”