Nanocomposite Hard Coatings: Deposition Issues and Validation of their Mechanical Properties

Abstract

The limitations of conventional coatings due to inferior hardness or poor oxidation stability can be overcome by nanocomposite hard coatings such as nc‐TiN/a‐SiNx, which consists of nanocrystalline TiN and a non‐crystalline tissue phase of SiNx which are mutually immiscible. The properties of nanocomposite coatings, especially their increased hardness, can be explained by their nanostructure, which leads to a maximum hardness at typically 80 atomic percent of the crystalline phase. We show that enhanced hardness can only be attained when the silicon nitride phase is sufficiently nitrided. The accurate and reliable measurement of the hardness and elastic modulus requires the use of appropriate nanoindentation equipment and a careful tip correction with periodical validation. It is shown that for a correct hardness determination of a few microns thick nanocomposite coatings, an indentation depth of 100 nm is sufficient. The maximum hardness of our nc‐TiN/a‐SiNx coatings deposited by a hybrid UBM/arc‐PVD process is about 40 GPa. This value represents a global hardness value, due to the nanocomposite structure there may be a local hardness variation of about ±10 %.

Properties of Flame Sprayed Ce0.8Gd0.2O1.9‐δ Electrolyte Thin Films

“…Hardness and elastic modulus have been calculated by nanoindentation measurements (Nanoindenter XP, MTS, Oak Ridge TN, USA) using the Oliver–Pharr algorithm 63. Some considerations included in the nanoindentation measurements are the following: Nanoindentation of a soft material (like CGO) on a hard substrate (like sapphire) should not be influenced by the substrate throughout the whole thickness of the film,64 but to ensure trustful results the indentation depth was limited to about 10% of the film thickness 65. Furthermore, a single nanoindentation measurement (load‐displacement curve) provides information on elastic deformation only locally,64 due to the polycrystalline microstructure of the CGO films.…”

“…Some considerations included in the nanoindentation measurements are the following: Nanoindentation of a soft material (like CGO) on a hard substrate (like sapphire) should not be influenced by the substrate throughout the whole thickness of the film,64 but to ensure trustful results the indentation depth was limited to about 10% of the film thickness 65. Furthermore, a single nanoindentation measurement (load‐displacement curve) provides information on elastic deformation only locally,64 due to the polycrystalline microstructure of the CGO films. Therefore several single load‐displacement curves (about twenty) with a load of 1 mN were obtained and the average value of hardness and elastic modulus were calculated.…”

“…Nanoindentation experiments were performed at different regions of the samples’ surfaces to avoid surface effects in the case of neighbouring indentations. Furthermore, low roughness values are required for determining with high accuracy values of hardness and elastic modulus 64, 66. Electrical characterization was performed by in‐plane four‐point DC conductivity measurements in ambient air, using similar configuration with 58.…”

The Critical Raw Materials in Cutting Tools for Machining Applications: A Review

“…Hard nanocomposite coatings for cutting tools may generally be classified into two groups: [137], nc-TiC + a-C [138,139] Ti-Si-N [140,141], Ti-Si-B-C [142][143][144], Ti-Si-B-C-N [145], AlTiN-Ni [146], ZrN/SiN x [147], nc-W 2 N/a-Si 3 N 4 [148], (Zr-Ti-Cr-Nb)N [149,150], Mo 2 BC [151], nc-AlN/a-SiO 2 [152]. In particular, several of these coatings, such as Ti-Al-Si-N, Ti-Si-N and AlTiN-Ni, were deposited and tested on cemented carbide WC-Co-based substrates like in [135,136,140,146].…”

The Influence of Layers Thickness on the Structure and Properties of Bilayer Multiperiod Coatings Based on Chromium Nitride and Nitrides of Transition Metals Ti and Mo

“…Nitrides of transition metals such as TiN [1], ZrN [2], MoN [3], CrN [4], TiAlN [5] and TiZrSiN [6] are widely used as protective coatings for cutting tools, parts and mechanisms of various functional purpose because of their high hardness and wear resistance [7,8]. In addition, coatings such as CrN also have a high resistance to oxidation, wear and corrosion [9,10].…”