Physical Vapour Deposition CrN Research Articles

Contribution of galvanic coupling with TiN, TiAlN, and CrN to the corrosion of steel in neutral and acidic chloride solutions

AbstractThe inherent defective morphology of the physical vapor deposition (PVD) hard coatings limits their corrosion protective ability. We examined the impact of nitride‐based PVD coatings, including TiN, TiAlN, and CrN deposited on inert substrates by cathodic arc PVD method (CA‐PVD), on the galvanic corrosion of carbon steel. Their contribution was evaluated by zero‐resistance ammeter (ZRA) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl at pH 2 and 6, with and without aeration. The results indicated the prominent role of the coating type and the coupling environment on the generated galvanic currents. Immersion tests for the TiN‐, TiAlN‐, and CrN‐coated steel cross‐sections visually verified these results. The galvanic current contribution was distinct in environments where oxygen reduction is the dominant cathodic reaction. However, the layers' contribution to galvanic corrosion was minimal in deaerated acidic solutions, which is attributed to the high bonding strength of adsorbed intermediates to the coating surfaces.

Influence of plasma nitriding pre‐treatment on the corrosion and tribocorrosion behaviours of PVD CrN, TiN and AlTiN coated AISI 4140 steel in seawater

AbstractCrN, TiN and AlTiN coatings were applied by the Physical Vapour Deposition (PVD) method on AISI 4140 and plasma nitrided (PN) AISI 4140 steel. The study aimed to investigate the effect of plasma nitriding before PVD on the corrosion and tribocorrosion behaviour of AISI 4140 steel in seawater. The electrochemical corrosion behaviour of the samples was evaluated in natural seawater by the potentiodynamic polarisation method. Tribocorrosion tests were performed against alumina in natural seawater under 5 N load and open circuit potential (OCP) using a ball‐on‐disk tribometer coupled with an electrochemical cell. As a result of the study, plasma nitriding applied before the coating significantly improved corrosion and tribocorrosion resistance of PVD CrN, TiN and AlTiN coatings. Besides, it was concluded that duplex treated low alloy AISI 4140 steel could be a candidate instead of stainless steel in tribocorrosion conditions for the marine environment.

Industrial evaluation of duplex PVD hard coatings for HPDC

During high pressure die casting (HPDC), molten metal is injected into the tool cavity where it reaches high velocities that cause substantial wear of the tool components. In order to mitigate this problem, different surface treatments are sometimes employed for high production tools. The most common treatments are nitriding and physical vapor deposition (PVD) of hard coatings. Within this study, effectiveness of two duplex PVD hard coatings, CrN and TiAlN, was tested on core pins, which are the most endangered elements of high pressure die casting tools. Core pins were tested in four industrial production runs of an automotive component. In every run, the tool was mounted with one pin that was PVD-coated, and one that was gas-nitrided. Nitrided core pins were used as a base standard since the nitriding is the most commonly used surface treatment. TiAlN-coated pins were able to complete a full production run of 22,000 shots without significant damage. CrN coating showed somewhat higher soldering tendency and erosion rates. Considering that the untreated core pins were able to withstand only 5500 shots, it can be concluded that duplex PVD coatings can significantly improve tool lifetime. Additionally, results indicate that often disregarded variances in casting temperature or in cleanliness of ingots used in production can significantly influence wear performance of HPDC tools. Analysis of the production costs has shown that the application of duplex TiAlN coating on the core pins can lead to significant savings for tested automotive components.

Effect of Surface Wear on Corrosion Protection of Steel by CrN Coatings Sealed with Atomic Layer Deposition.

Corrosion protection of steel obtained with physical vapor deposition (PVD) coatings can be further improved by sealing the intrinsic pinholes with atomic layer deposition (ALD) coatings. In this work, the effect of surface wear on corrosion protection obtained by a hybrid PVD CrN/ALD Al2O3/TiO2 nanolaminate coating was studied. The samples were investigated by alternating surface wear steps and exposure to salt solution and consecutively the progression of corrosion after each wear and each corrosion step was evaluated. Optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectroscopy showed that the rust spots were almost exclusively located on positions at which the wear steps had removed the top surface of the PVD CrN coating. Nevertheless, even after complete removal of the ALD nanolaminate from the top of the CrN surface by sandpaper grinding, the corrosion current density was less than half compared to the PVD CrN coating alone without surface wear. Cross-sectional SEM images obtained with focused ion beam milling showed not only the presence of the ALD coating at the CrN defects but also the opening of new pathways for the corrosion to attack the substrate. A mechanism for the effect of wear on the structure and corrosion protection of hybrid PVD/ALD coatings is proposed on the basis of this investigation.

An investigation into the tribological performance of Physical Vapour Deposition (PVD) coatings on high thermal conductivity Cu-alloy substrates and the effect of an intermediate electroless Ni–P layer prior to PVD treatment

The use of high thermal conductivity copper alloys in plastic injection moulds provides the benefit of rapid moulding cycles through effective heat transfer. However, copper alloys are relatively soft and wear rapidly so manufacturers are now developing copper alloys with increased hardness and wear resistance. Their wear resistance can be further improved by the deposition of hard coatings such as electroplated chromium, electroless nickel and Physical Vapour Deposition (PVD) coatings. In this paper, the tribological performance of three proprietary high-strength Cu alloys (Ampcoloy® 940, Ampcoloy® 944 and Ampcoloy® 83) coated with PVD CrN and CrAlN coatings has been evaluated. A medium phosphorous content electroless Ni–P (ENi–P) plated layer was also deposited as a pre-treatment to PVD CrN and CrAlN coatings to increase the load support. The effect of this intermediate ENi–P layer was also evaluated. Surface roughness and instrumented hardness measurements were used to characterise all coated systems in both plated (i.e. with the intermediate ENi–P coating) and standard (i.e. unplated) conditions. Scratch tests were also performed to evaluate the effect of the ENi–P on PVD coating adhesion to Cu alloy substrates. The tribological behaviour of PVD-coated Cu alloy systems was evaluated by pin-on-disc wear tests and ball-on-plate impact tests. Results demonstrate that the ENi–P layer improves the load support for PVD coatings on Cu alloys, thereby improving their tribological performance. However, for PVD-coated Cu alloys in the standard condition, the Cu alloy substrate type plays an important role in the tribological performance of PVD coatings. For instance, PVD CrN coatings were more suited to a certain Cu alloy type whilst CrAlN to the other two types.

Effect of Ni Interlayer on Corrosion Behaviour of Crn Pvd Coating Deposited onto Plastic Mould Steels

The plastics industry commonly uses moulds made of steels containing MnS inclusions. These inclusions play the role of heterogeneities, which make manufacturing easier. Moreover, these types of alloy are thermal treatment free, cheap, and easily available. Unfortunately, their use in corrosive conditions is prevented owing to the poor corrosion behaviour of the MnS particles. In order to mask these highly sensitive inclusions and to enhance the surface mechanical properties, hard physical vapour deposition (PVD) CrN coatings, elaborated at two different temperatures, have been used. The coated specimens have been tested in saline corrosive solutions using electrochemical techniques. Corrosion results from dissolution of the anodic substrate through coating porosity, inherent to the PVD process, which leads to the deposit peeling off. The aim of the present study is to determine the corrosion resistance of an underlayer electroless nickel deposited coating on a 40CrMnMo8S substrate coated with PVD CrN.

PVD coatings as an environmentally clean alternative to electroplating and electroless processes

Today the development of clean technologies in all spheres of industrial manufacturing is an essential task, not only for material and metal finishing but also for plasma surface engineering. Among the most critical group of technologies which needs to be replaced by alternative technologies are processes used to produce functional galvanic and decorative coatings. The electroplating of finishes, such as hard chromium, cadmium and nickel in metal finishing is today recognized as a major source of environmental pollution in every country. Therefore wet bath technologies have started to lose favour compared with high performance dry coating methods such as physical vapour deposition (PVD), plasma-assisted chemical vapour deposition, chemical vapour deposition and thermal spraying. Among these techniques, the results obtained with PVD coatings in metal cutting and forming in the last 15 years show the most promising solution of the complicated situation in which galvanic coatings seemed to be technologically and economically irreplaceable.In this paper the general situation in this field is shown. Already today it is possible to replace efficiently some of the galvanic processes in specific cases (e.g. Cr, Ni, Cd, Zn, Au). It is important to point out that PVD is considered to be a technique which can provide not only metallic, but also alloyed and ceramic coatings with a virtually unlimited range of chemical composition and therefore controlled protective, mechanical and wear-resistant properties. Entering into competition with galvanic coatings the manufacturers of PVD coaters were confronted with new requirements: a huge quantity of substrates of the same size, to be chemically and plasma cleaned and then coated at the highest possible deposition rate. For industrial mass production one can therefore use only large PVD batch systems or in-line coaters. The alternative for today's low price galvanic coatings is therefore dry and clean PVD technologies, fully supported by legislation on environmental protection. The economics depend directly on the substrate type and the quantity.The first positive results on the replacement of electrodeposited nickel on aluminium substrates and hard chrome on soft iron are also reported here. A soldering test was made on a sputtered nickel layer. Wear and corrosion tests were performed with iron cores, coated with PVD CrN coating. All tests were made in the Slovenian automotive industry. Results show that for a large number of substrates PVD clean technology is already economically competitive with galvanic coatings.