Optimization of Cr-Al-N coating by multilayer architecture with TiSiN insertion layer

Multilayer architecture is a promising approach to tailor the structure and properties and attracts broad research interests. Here, we prepared TiSiN/CrAlN_1 and _2 multilayer coatings with a similar bilayer period and varied modulation ratios as well as referential Ti0.87Si0.13N and Cr0.32Al0.68N monolithic coatings to compare their structure and thermal properties. The TiSiN/CrAlN_1 and _2 coatings, which allow for an epitaxial growth of TiSiN layers on CrAlN layers, show hardness values of similar to 36.1 and 38.2 GPa, respectively, corresponding to similar to 38.6 GPa for Ti0.87Si0.13N coatings and similar to 27.3 GPa for Cr0.32Al0.68N coatings. The introduction of TiSiN insertion layer into Cr-Al-N coating improves the thermal stability via deferring the w-AlN formation and N-loss, but has an adverse impact on the oxidation resistance. Compared to Cr0.32Al0.68N, the onset temperatures of w-AlN formation of TiSiN/CrAlN_1 and _2 are higher by similar to 100 degrees C and 200 degrees C, respectively, and the N-loss is retarded by similar to 200 degrees C in multilayer coatings. After 10 h exposure to air at 1000 degrees C, the oxide scale of Cr0.32Al0.68N coating is similar to 0.20 mm, whereas the TiSiN/CrAlN_1 and _2 coatings exhibit thicker oxide scales with thickness of similar to 0.53 and 0.78 mm, respectively. (C) 2017 Elsevier B.V. All rights reserved.