Monolithic and multilayer Cr/CrN, Cr/Cr2N, and Cr2N/CrN coatings on hard and soft substrates

Abstract

Using controlled low-energy ion bombardment, CrN and Cr2N films were reactively sputtered from a Cr target in a mixed Ar-N2 discharge. Various Cr-N based coating architectures were developed in this work to provide better substrate accommodation than is currently available using monolithic CrN or Cr2N, as well as to build in “load support” for the hard surface layers on more compliant substrates. A series of monolithic and multilayer structures were deposited at low temperatures (<200 °C) to examine the advantages and disadvantages of various coating architectures and ion energies on three substrates: A2 tool steel, 52100 stainless steel, and 2024-aluminum. The optimal operating point for deposition of stoichiometric CrN and Cr2N coatings was determined from analysis of the target state, and supported by in situ ellipsometric measurement of the optical properties of the films during growth. Films were characterized using X-ray, scanning electron microscopy and Rutherford backscattering spectroscopy. Their properties have been evaluated by microhardness, scratch adhesion, and pin-on-disk wear testing. Many of the multilayer coatings gave microhardness values in excess of 2000 HK, often having better adhesion than the single layer films. This was reflected in the wear performance of these films on both A2 and 2024-Al, where no measurable wear was observed in severe dry sliding wear over sliding distances of more than 9000 m against a WC ball. Thus, wear-resistant Cr-N film architectures can be used on some temperature- sensitive and/or compliant substrates to significantly enhance their surface properties.

Optimization of multilayer wear-resistant thin films using finite element analysis on stiff and compliant substrates

“…Displayed in Figure 7 is the optimized structure compared to an empirically designed structure that has been successfully tested, 5 as well as a nonoptimal solution obtained by multiobjective optimization using GA. It was observed that the optimal solution obtained had a strain value approximately 0.5% less than one of the nonoptimal solution tested in the optimization iterations and appears to be a "better" design, in terms of the measures used here as objectives and constraints, than the most successful empirically developed coating.…”

“…The past decade has seen a tremendous growth in the utilization of CrN films because of their reduced residual stress, improved oxidation resistance at high temperatures, and lower coefficients of friction when compared to TiN films. [1][2][3][4] Recently, our focus has shifted to Cr/CrN multilayer films, 5 which can be very effectively used to further improve the fracture toughness, hardness, and adhesion of these films. 6 Design of an optimal multilayer coating structure requires a detailed knowledge of the stress/strain profiles produced within the multilayer coating structure under mechanical loading.…”

Design of Transition-Metal Nitride Thin Films for Thermoelectrics

“…For such purposes CrN has excellent mechanical properties such as high hardness (∼28 GPa), high corrosion resistance, and excellent wear properties. [136][137][138][139][140][141][142] CrN is easy to synthesis as a thin film by magnetron sputtering (DC, pulsed DC, middle frequency RF, or High Power Impulse). [141][142][143][144][145][146][147] CrN thin films can be grown with a very low internal stresses, thus it can be synthesized in various thickness from thin to thick coatings (100 nm to 100 µm) on a variety of steels and engineering ceramics with very good adhesion.…”

Optimization Of Multi-Module CrN/CrCN Coatings

“…The results of calculation are consistent with the experimental results of the coating's optimization obtained by Kuruppu al. [21]. In turn, in [22] was optimized the geometry of multilayer TiN /TiAlN deposited on the substrate HSS (High Speed Steel) previously coated with metallic chromium.…”