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Über dieses Buch

This book describes current, competitive coating technologies for vehicles. The authors detail how these technologies impact energy efficiency in engines and with increased use of lightweight materials and by varying coatings applications can resolve wear problems, resulting in the increased lifecycle of dies and other vehicle components.



Chapter 1. Energy Consumption Due to Friction in Motored Vehicles and Low-Friction Coatings to Reduce It

During the past two decades, global awareness and societal needs for more fuel-efficient and environmentally friendly transportation systems have increased considerably because of the diminishing oil reserves, skyrocketing fuel prices, and much tougher governmental regulations to combat greenhouse gas emissions. During the same period, automotive and lubrication engineers have intensified their efforts to reduce parasitic energy losses due to friction, rolling resistance, aerodynamics, and cooling systems and to thereby boost the efficiency of next-generation transportation vehicles. In comprehensive studies involving light, medium, and heavy-duty vehicles (Holmberg et al., Tribol Int 47:221–234, 2012; Holmberg et al., Tribol Int 78:94–114, 2014), it was determined that nearly one-third of the fuel energy is consumed to overcome friction generated by engines, transmissions, tires, and brakes. Among these, energy losses due to friction in engines and transmissions were reported to be among the highest. The same studies have also advocated that with the adaptation of advanced friction control technologies, energy losses due to friction could be reduced markedly, and such improvements in energy efficiency can, in turn, translate into significant reductions in greenhouse gas emissions. The main purpose of this chapter is to provide an overview of the impact of friction on energy consumption in vehicles on a global scale and of the recently developed and emerging friction control technologies that can further improve the fuel efficiency and eco-friendliness of future transportation vehicles.
Ali Erdemir, Kenneth Holmberg

Chapter 2. Diverse Coatings for Engine Parts

The focus of recent attention in automotive field is on low friction and wear resistant coatings (e.g., (Si-)DLC, TiAlCrSiCN, polymer) for use in powertrains and thermal spaying applications. As a future perspective, the development of advanced coating materials and processes will be steadily required to enhance quality and functionality of parts being coated and to reduce process time and cost. Concerted research effort converging coatings with surface patterning and finishing is necessary to maximize the overall functionality and performance of engine parts.
Sung Chul Cha

Chapter 3. Overview of DLC-Coated Engine Components

Fuel-saving technologies have become more important in recent years, especially for automobiles, in order to avoid global environmental destruction and global resource depletion. In addition, the use of toxic elements such as phosphorus, sulfur, and chlorine in industrial lubricants must be decreased or eliminated. Technologies for reducing friction with environmentally friendly materials are direct ways of addressing environmental problems. Diamond-like carbon (DLC) coatings are increasingly being applied to the sliding parts of automotive engines, among other applications, to reduce friction and wear. These coatings have several advantages, including their harmless nature to the human body because they consist mainly of carbon, low friction, high wear resistance, and strong corrosion resistance.
This chapter discusses recent topics concerning the application of DLC coatings to automotive engine components. DLC coatings have already been successfully applied to the valve lifters and piston rings of mass-produced gasoline engines. The resultant effect on reducing friction in each application is described briefly. The effect of engine oil additives on the friction and wear properties of DLC coatings is also explained. Promising technologies for applying DLC coatings to future engine components are then presented.
The first topic discussed in this regard is the application of DLC coatings to aluminum alloys with sufficiently strong adhesion for obtaining high wear resistance. This can be accomplished by shot peening the aluminum alloy substrate with fine tungsten particles. A DLC coating deposited on A2017 and A5052 aluminum alloys (Japanese Industrial Standards) with this new process showed 40–80 % higher wear resistance and adhesion strength than DLC coatings formed by conventional processes. As a result, a DLC-coated aluminum alloy piston displayed superior wear resistance compared with that of a noncoated piston in a short-term engine firing test.
The second topic concerns super-low friction properties obtained by combining a DLC coating with an environmentally friendly lubricant. A super-low friction coefficient below 0.01 was obtained with a self-mated ta-C (tetrahedral amorphous carbon) coating lubricated with oleic acid, whereas an a-C:H (amorphous hydrogenated carbon) coating and bearing steel (JIS-SUJ2) did not display such a large reduction in the friction coefficient. This result implies that automotive engine fuel economy can be improved markedly by using completely environmentally friendly materials. These advanced technical results indicate that expanding the application of DLC coatings to various automotive components and mechanical parts used in other industries would be a promising approach for addressing global environment problems.
Makoto Kano

Chapter 4. Coating Technologies for Automotive Engine Applications

Coatings are materials deposited on surfaces to enhance a specific set of performance attributes, i.e., wear resistance, erosion resistance, corrosion resistance, friction reduction, etc. Since wear, corrosion, and friction phenomenon are restricted on the surface, deposition of a coating provides a great flexibility in imparting properties which could be significantly different from the parent material. There are wide varieties of materials available for deposition and the choice of a material depends on the application, compatibility with the base material, and the deposition process. This chapter first reviewed lubrication regimes in critical tribological contacts (cam and tappet in valvetrain, piston and piston rings and cylinder bore, piston pins, and bearings) in an engine to justify where coatings could improve friction reduction and durability. Then, described coatings being used/explored in each of these applications followed by an outlook of coating technologies in future automotive engines.
Arup Gangopadhyay

Chapter 5. Customized Coating Systems for Products with Added Value from Development to High-Volume Production

Modern components and systems for automotive and industrial applications have to meet various requirements in multiple technical fields. Apart from properties that affect the part itself—like geometry, stiffness, weight, or rigidity—the surface properties must be adjusted to the growing environmental requirements. Therefore, coatings are increasingly applied to reduce the friction losses of car components, improve fuel efficiency, and reduce CO2 emissions. This article describes how to use surface technology as a modern design element for components and systems to enable the demanding requirements on market-leading automotive and industrial products. Therefore, Schaeffler has developed and established a coating toolbox for customized surfaces to deliver the right solutions for all that needs and requests with the corresponding coating system enabled by PVD/PACVD, spraying, or electrochemical technology. For innovative products, it is extremely important that coatings are considered as design elements and integrated in the product development process at a very early stage. In this article, tribological coatings are viewed within a holistic and design-oriented context. The latest developments of amorphous carbon coatings and their characteristics and the technical and economical effects of their use in combustion engines and industrial bearing applications are described. The presented Triondur® amorphous carbon-based coating systems (a-C:H, a-C:H:Me, a-C:H:X, and ta-C) are excellent examples for customized tribological systems like bucket tappets or roller bearings. These carbon coatings offer the following advantages: super low friction with highest wear resistance, customized surface energy, optimized wet ability and interaction with formulated engine oils, and low adhesion to the counterpart.
A close collaboration between designers and surface engineers is required in the future. Schaeffler delivers around 100 million high-quality PVD- and (PA)CVD-coated components every year that enable outstanding applications, preserve resources, and meet increasing customer requirements.
T. Hosenfeldt, Y. Musayev, E. Schulz

Chapter 6. Surface Treatments for Automotive Applications

Advanced surface treatments are used more and more in daily manufacturing of parts for the automotive industry to serve functional and decorative purposes. Higher specific loads (thermal, mechanical, etc.), weight and friction reduction, longer components lifetime, and improved corrosion resistance are demanding for modern automotive systems. Within the last decades, high-performance surface solutions and new or improved surface treatments, especially in the group of plasma-assisted processes, both for diffusion and deposition processes were developed to provide economic applications for automotive parts. The surface treatments PVD, PACVD, thermochemical heat treatment, and thermal spraying will be briefly described. In addition, the combination treatment involving at least two different treatments will be discussed. It will be shown that these new treatments are becoming more common in engine applications and power train. The potential of optimized functional surface generation is demonstrated both for different types of substrate materials (e.g., Al alloys, sintered steels, case-hardened steels, etc.) and part geometry (e.g., cylinder bores). Due to the fact that an enormous wide property field of surfaces is adjustable within these competing surface treatments, it becomes common to substitute the more limited traditional treatment-substrate systems (e.g., galvanizing, electroplating etc.) with the described advanced treatments. Besides a general description of the surface treatments and their main application aspects, the internal coating of bores inside the engine by plasma spraying, the increased corrosion protection of power train parts by the IONIT OX process as well as piston ring treatments, and the widespread potential for DLC coatings are discussed in more detail.
Jörg Vetter

Chapter 7. Hard Coatings and Coating Processes for the Automotive Industry

Thin film coatings have over the years found a way into a variety of applications in the automotive industry. First applications of carbon-based coatings (DLC) were introduced for fuel delivery systems in the mid-1990s, followed by engine components a few years later. DLC coatings for fuel injection components and engine components such as valve tappets, cam followers, and piston pins represent the bulk of the mainstream applications and have become a de facto standard for many automotive manufacturers. The next generation of coatings for the automotive industry will be designed to interact with additives in fuels and engine oils. Of particular interest are tribo-chemically active coatings, which promote the formation of beneficial tribological films. Besides carbon-based coatings, the chapter reviews coating applications in turbochargers. The turbochargers are very efficient devices to boost power output of combustion engines, thus enabling engine downsizing and respective gain in fuel consumption. Due to the unique operating conditions, turbochargers are exposed to various mechanical challenges at normal and elevated temperatures. Potential applications of hard coatings for wear protection in turbochargers are reviewed. Finally, an application of hard coatings for manufacturing technology of catalytic converters and diesel particulate filters is discussed.
André Hieke, Val Lieberman, G. J. van der Kolk

Chapter 8. Machining and Characterization of Functional Surfaces of Thermal-Coated Cylinder Bores

Machining of thermal-sprayed layers is a new challenge for machining cylinder bores with different honing variants. New strategies for machine and tool layouts as well as in particular the availability of appropriate diamond stones considering the material-specific properties of the cutting process are essential. Based on the coating material characteristics which are relevant for machining, a new honing process is presented.Following the material properties of thermal-sprayed layers, the machining task, the process layout and the obtained quality values are described. Also the different variants of machining strategies are indicated, which are applicable for the different thermal-sprayed layers. The paper describes the machining results regarding the functional properties.
Gerhard Flores, Andreas Wiens, Manuel Waiblinger

Chapter 9. Coatings for Aluminum Die-Casting Dies

Aluminum die-casting dies are subject to severe loads, thermal softening, and shock as well as high-temperature wear and oxidation at temperatures exceeding 750 °C. Collectively, these decrease die’s life cycle and increase production costs of aluminum parts. The objective of this work is to develop outstanding coating materials which can prolong the die’s life cycle by more than 200 %. Specifically, in this study, we compared the critical properties (i.e., Al adhesion, thermal shock, stability, etc.) of 11 coatings, and subsequently, three best coatings are selected to be applied in production lines and evaluated for their overall performance and durability. The best performing coating TiAlCrSiCN is then characterized in terms of its nanolayered design, constituent elements, coating process, and effects. Especially, this and other newly developed coatings on conventional die material (SKD61) could be used as a substitute for more expensive high-temperature die materials.
Sung Chul Cha

Chapter 10. Coatings for Forming Dies of Advanced High-Strength Steel

Recently, most of the automobile companies and related industry increased their efforts in further increasing the safety and in reducing the weight of car body and chassis parts by using advanced high-strength steel sheets. Traditional hard coatings used in forming dies cannot fulfill the required wear resistance and durability. The coatings for the 980 MPa class forming dies need to have complex material performance like wear, temperature, and fatigue resistance as well as low-friction behavior. In order to develop the newer and higher-performance coatings for such forming operations, the ideas of carbon doping or carbon overlay coating should be considered for low-friction behavior in current dies. Furthermore, toughness, fatigue resistance, and strong bonding properties should be further improved through nitriding and followed up with multilayers of CrN, TiN, etc. In this work, TiAlCrCN and AlTiCrN + CN showed high promise among 18 coatings considered, and these should be considered for use on future drawing dies. Ultimately, the enhanced coatings or layer design with much refined nanograins and nanolayers can be developed for applications requiring the forming of much higher-strength steels (i.e., ultrahigh-strength steels or 3rd generation AHSS sheets) and of more complicated shapes.
Sung Chul Cha

Chapter 11. Diamond-Like Carbon Coatings with Special Wettability for Automotive Applications

Surface modification is an effective way of improving the tribological properties of base materials and is now actively being used in the automotive industry. Surface wettability can affect the overall performance of automotive components, such as windshields and mirrors, and controlling the surface hydrophobicity or hydrophilicity has been a major focus of research work in this industry. Diamond-like carbon (DLC), which is an amorphous carbon compound with outstanding mechanical and tribological properties, has gained considerable attention as a superior functional coating material and has been successfully applied to a range of mechanical automotive components, leading to better performance and durability. Recently, DLC-based materials with special wettability have been successfully used for the development of superhydrophobic and superhydrophilic surfaces, and a variety of industrial as well as biomedical applications have been proposed. Undoubtedly, being able to control the surface wettability using such DLC-based materials with tunable wettability would expand the original capabilities of the materials used in the automotive industry today. In this chapter, after giving a brief introduction to the fundamentals of surface wettability in relation to DLC coatings, we review recent studies on the control of surface wettability using DLC-based materials and then discuss future outlook.
So Nagashima, Myoung-Woon Moon

Chapter 12. Smart Surfaces for Lubrication: Solid Lubricants and Adaptive Texture

Modern thin films, although still being developed at laboratory scale, promise revolutionary changes in surface engineering. For automotive industry, we will focus on two classes of thin films with the potential to decrease or even eliminate oil additives, reduce friction, and improve control of tribological process.
T. Polcar

Chapter 13. Decorative PVD Coatings on Automotive Plastic

The CO2 emission regulations have an increasing impact on the automotive industry, as these regulations are connected with severe penalties in case the average fleet emission is exceeding the limits for Europe, as imposed by the European Commission. These measures are enforcing the automotive industry to a significant increase in fuel efficiency. Basically, the emissions can be reduced, by reducing the wear losses in the powertrain and by reducing the weight of the cars, by using more and more plastic materials. Many of these parts do also have a decorative function and therefor are Chrome plated. As the plating process has to handle heavy poisoning liquids and consumes a lot of water, the industry is looking for green low cost alternatives. In this chapter the Cromatipic® process is introduced which combines a painting with a PVD coating and fulfils all requirements of the automotive industry for interior and exterior decorative parts. Finally will be introduced an integrated inline factory for performing the Cromatipic® process very cost effective.
Thomas Krug, Roel Tietema


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