Physical Vapor Deposition (PVD) Coatings and Sustainability: A Green Alternative to Traditional Coatings

Traditional coatings are materials that are applied to surfaces to improve their functionality, durability, and appearance – from basic infrastructure to industrial tools to everyday consumer goods. These coatings have been used for hundreds of years, and they include a variety of natural and synthetic materials such as paints, varnishes, enamels, and lacquers.

On the other hand, physical vapor deposition (PVD) coatings are formed by vaporizing solid materials in a vacuum environment and then allowing the vaporized particles to condense onto the substrate, creating a thin film. The main difference between traditional coatings and PVD coatings is in the way they are applied and the properties they offer.

It must be said that compared to traditional coatings, PVD coatings are more expensive and more difficult to prepare due to process complexity, the need for special deposition equipment, and material costs. However, in terms of sustainability, these coatings offer several benefits compared to traditional coating methods. In the following points, there are some aspects contributing to their sustainability.

PVD coatings are thin films, typically ranging from a few nanometers to several micrometers in thickness. Traditional coatings require thicker layers and thus, PVD coatings use significantly less coating material. This leads to reduced resource material consumption and waste generation.

The source material for cathodic arc deposition (or Arc-PVD) and magnetron sputtering is typically in the form of circular or rectangular targets of a pure metal or metal alloy (Ti, Cr, AlTi, … ). However, a huge number of solid chemical compounds can be used as the sputtering target, but in some cases (non-conductive materials, magnetic materials), special techniques must be used. Especially sputtering targets are not consumed uniformly, and therefore the recycling of used eroded targets is an important sustainability factor.

For different applications and uses, PVD coatings with unique and tunable properties can be designed and manufactured by changing deposition parameters and chemical composition. Thanks to such flexibility, coatings can offer desired properties, including extreme hardness, a low friction coefficient, thermal or chemical stability, ultra-low roughness, or wear resistance.

Here are examples of some of the most commonly used coatings and their typical applications:

TiN – A versatile wear-resistant coating for many applications with an eye-catching gold color. Biocompatible and food-safe coating.

TiAlN – A high-performance coating that gives excellent protection against abrasive wear and tool erosion. Suitable for plastic injection molding, saw blades, and the forming of high-strength metal sheets.

AlTiN – A universal coating solution for a wide range of applications and tools thanks to its high resistance to crater wear and oxidation.

TiSiN – Superior oxidation resistance and thermal stability, with exceptional wear resistance for machining difficult-to-cut materials.

TiCN – Higher wear resistance than TiN, good toughness, and a low coefficient of friction provide effective resistance against wear. Used for taps, thread forming, punching, and metal forming.

TiAlCN – A coating solution for injection molding, die casting, saw cutter, and other.

AlTiCrN – Improved coating structure of multilayered coating for roughing operations provides higher stability of the cutting edge with prolonged tool life.

PVD coatings provide enhanced wear resistance, corrosion resistance, and durability to coated surfaces. By protecting them from degradation and extending their lifespan, PVD coatings can significantly contribute to reducing the maintenance, repair, or replacement of components, leading to a reduction in material consumption, energy use, and waste generation over time.

Industrial systems become more complex, more sensitive, and more vulnerable to failures and breakdowns. Reliability is therefore of increasing importance. The failure may result in safety risks for people, and breakdowns in the production process are expensive both for producers and for energy suppliers.

One of the main reasons for shut-downs and failures is connected with tribology, including wear and friction-related events. In terms of product lifespan and reliability, PVD coatings bring significant improvements in a wide range of applications.

If the fabrication processes are optimally designed, PVD coating manufacturing can be highly energy-efficient compared to traditional coating methods. The deposition occurs in a vacuum environment, which allows for precise control over the deposition process, resulting in minimal material waste and energy usage.

Volatile organic compounds (VOCs) are organic compounds that have a high vapor pressure at room temperature. They are responsible for the odor of perfumes as well as pollutants. Some are dangerous to human health or cause environmental harm. VOCs are commonly found in many traditional coating processes and can contribute to air pollution and health concerns. PVD is a dry and vacuum-based process that eliminates the use of liquid solvents and the associated VOC emissions, resulting in improved air quality and worker safety.

PVD coatings are generally applied to metallic or other recyclable substrates. The thin nature of the coatings allows removal through processes like stripping, blasting, or etching, facilitating the recycling or re-usability of the coated components or substrates. However, these processes can use different harsh chemicals, which require environmentally responsible handling.

While PVD coatings offer sustainability advantages, it is important to note that the overall sustainability of a coating process also depends on factors such as the energy source used, waste management practices, and the responsible disposal of coating byproducts. Implementing proper process controls, optimizing energy usage, and adhering to environmentally responsible practices are crucial for maximizing the sustainability benefits of PVD coatings.

To conclude, PVD coatings are a promising green alternative to traditional coatings in many more or less challenging applications. In terms of sustainability, these coatings offer several benefits compared to traditional coating methods, including resource and material efficiency, enhanced performance, extended product lifespan, improved reliability, energy efficiency, reduction in emissions, and recyclability. However, proper process control and responsible practices are crucial for maximizing green benefits.

Holmberg, A. Erdemir, Influence of tribology on global energy consumption, costs and emissions

K. Holmberg, Reliability aspects of tribology

B. Navinsek, P. Panjan, I. Milosev, PVD coatigns as an environmentally clean alternative to electroplating and electroless processes

H. van Lente, J.I. van Til, Articulation of sustainability in the emerging field of nanocoatings

T. Rajmohan et al., Eco Friendly Machining Processes for Sustainability – Review

J. Grewal, C. Hauptmann, G. Serafeim, Material Sustainability Information and Stock Price Informativeness

M.F. Cunningham et al., Future green chemistry and sustainability needs in polymeric coatings

R. Nartita, D. Ionita, I. Demetrescu, Sustainable Coatings on Metallic Alloys as a Nowadays Challenge