Properties and Performance of TiAlSiN and AlCrN Monolayer and Multilayer Coatings for Turning Ti-6Al-4V

Abstract

The high chemical activity, low thermal conductivity, and high strength of titanium alloys lead to severe tool wear during cutting. The coating applied to the tool surface insulates the effect of heat and chemical reactions. TiAlSiN coating and AlCrN coating are two representative coatings with excellent properties in TiN-based and CrN-based applications, respectively. Three types of nanocoatings—TiAlSiN monolayer, AlCrN monolayer, and TiAlSiN/AlCrN multilayer—were prepared, and the microstructure, mechanical properties, oxidation resistance, diffusion properties with titanium alloy, and cutting performance of the coatings were investigated utilizing SEM, TEM, XRD, TGA, GD-OES, nanoindentation, and scratching instruments. The hardness, elastic modulus, and adhesion strength of TiAlSiN/AlCrN multilayer coatings are between TiAlSiN monolayer and AlCrN monolayer coatings, which meet the “law of mixtures”. Adhesion strength is the primary condition for cutting applications and should have a minimum threshold value. Ti and N elements are the most significant in the diffusion between coatings and titanium alloys. The nitride coating containing Cr aggravates the loss of N in contact with the titanium alloy. In addition, multilayer structural coatings can lead to more severe diffusion than monolayer coatings due to their inherent interlayer defects. Although diffusion between titanium alloys and coated tools is more severe than with other workpiece materials, the main factor affecting tool cutting life is still the H3/E*2 value determined by the hardness and modulus of elasticity together.

Enhancing Tool Performance in High-Speed End Milling of Ti-6Al-4V Alloy: The Role of AlCrN PVD Coatings and Resistance to Chipping Wear

“…Finite element modeling has been employed to verify the effect of the design of magnetron-sputtered multilayer Ti/AlN coatings on the distribution of residual stress [17]. However, it was also found that the multilayer AlCr/AlTi-based coating cannot prevent diffusion leading to a reduced tool life; instead, it may cause worse diffusion wear due to the interlayer defects compared to a AlCrN monolayer coating with a better adhesion strength to the substrate [18].…”

High-temperature tribological properties of AlCrN coatings deposited on textured surfaces under dry friction

“…In addition to the surface texture, surface coating can improve the surface friction properties. AlCrN coatings have been widely used in cutting tools owing to their excellent material properties, including high hardness, wear resistance, and chemical stability [14][15][16]. Mo et al [17] investigated the sliding friction properties of an AlCrN coating and discovered that it exhibited excellent wear resistance, with the primary friction mechanism being a combination of wear and oxidation.…”

Tribological Performance of Anti-Wear Coatings on Tools for Forming Aluminium Alloy Sheets Used for Producing Pull-Off Caps

“…Das et al [27] developed a nanocomposite AlTiSiN coating deposited using scalable pulsed-power plasma, which improved the surface finish of AISI D6 steel samples during turning. Liu et al [28] investigated the microstructure and oxidation resistance of three nanocoatings (TiAlSiN/AlCrN multilayer, AlCrN monolayer and TiAlSiN monolayer). It was found that the AlCrN coating has the highest adhesion strength, while the TiAlSiN coating has the lowest adhesion strength among the coatings tested.…”