**1. Introduction**

#### **1.1 Increasing demands on multifunctional nanocomposite coatings**

Recently, the industry demands the right property in the right place (application). It is well known the life span of the machinery could be increased and the new properties could be endowed through the application of proper coating systems. Therefore, attempts have been made to develop various coatings with properties suitable for mechanical parts in different applications. For example, a Swiss coating company, Platit, has developed over 100 various coating systems in order to get optimal performance according to the working functions of the tools and machine components [1]. In addition, a German bearing company, Schaeffler, has developed the customized surface technology in which the different coatings are designed for the different bearing systems and this resulted in the increased lifetime, increased functionality, and other added value to the systems [2]. Furthermore, the industry demands new coating systems with very different or opposite properties for the superior properties of the product. For instance, the new coating systems exhibit high hardness and low friction, or high conductivity and high corrosion resistance. To obtain such opposite properties in a single coating system, two or more phases of the coating material must be formed in the nanometer-scale area which is a nanocomposite coating. Therefore, new demands for nanocomposite coatings are gradually increasing.

As shown in **Figure 1**, nanocomposite coating can be divided into two types, hard matrix nanocomposite coating and soft matrix nanocomposite coating, depending on the matrix material. If the nanocomposite coatings could be formed by the combination of ceramic phases, such as nitrides and carbides, higher hardness, higher thermal stability, and the corrosion and oxidation resistance could be obtained. The properties are very useful for molds and tools. Up to the early twenty-first century, most of the commercialized nanocomposite coatings were made by a combination of ceramic phases. As a result, coatings with the super-hardness over 40 GPa, the ultra-hardness over 70 GPa, and thermal stability over 1100°C had been developed [3, 4]. The crystalline phase of the nanocomposite coating is nitride, carbide, boride, and oxide, and the amorphous phase may be metal or ceramic. In such a case, the properties of the

#### **Figure 1.**

*Two kinds of nanocomposite coatings are based on the matrix materials: Hard matrix and soft matrix.*

*Current Development of Automotive Powertrain Components for Low Friction and Wear… DOI: http://dx.doi.org/10.5772/intechopen.106032*

metal phases, such as high toughness, electric conductivity, and low friction, could be obtained with the properties of ceramic phases. Because of the wider spectrum of properties, including opposite properties, the soft matrix coatings could be used in various industrial fields.

In the early twenty-first century, a diamond-like carbon (DLC) coating has been used as a protective coating for various parts of the automobile engine. The engine performance has been greatly improved by adopting the low friction and high endurable coating. But automobile companies tried to adopt the new modified engine oils for better lubrication where the various additives are designed to have protective effects on the steel surfaces. But such additives have no compatibility with non-metallic coating and even they could damage DLC coatings [5]. Also the future demands on the internal combustion engine (ICE) systems and the application conditions of the mobility parts for the electric vehicles (EV) are much severe and worse. Future mobility shall be operated under non-lubrication conditions, which lead to more severe conditions for friction and wear of components. Consequently, new coating systems should be developed to have the better capability with the future automobile systems. Nanocomposite coating can be applied to future mobility parts.

#### **1.2 Preparation of the alloying targets for nanocomposite coatings**

The design rules for the nanocomposite coatings are discussed in the previous manuscripts [6, 7] but the most important basic rule is two elements are needed and they should be immiscible or low miscible properly each other [8]. Therefore, it is not easy to manufacture an alloying target made of an element that meets the requirements for depositing a nanocomposite coating by a general conventional target manufacturing method. The most commonly used method for the fabrication of a nanocomposite coating is a multi-cathode sputtering system that uses as many targets as additional elements [9]. However, in order to deposit a nanocomposite coating of a desired composition, it is necessary to control element targets having different sputtering yields to an appropriate power level, and to obtain a uniform coating, it is necessary to control various process parameters [10]. These complex equipment and process conditions hinder the mass production of nanocomposite coatings. In this study, an alloying target with high chemical homogeneity, high structural uniformity, and excellent mechanical properties was developed for the mass production of nanocomposite coatings.

The alloying target could be prepared generally by the preparation of the alloying powders and the subsequent sintering of the alloying powders, which is indexed as a red line in **Figure 2**. Because the alloying rules for nanocomposite materials are the same for the amorphous materials [11], the first attempts were made to find the proper alloys among amorphous materials and the target making procedures for the alloy systems with the amorphous compositions, such as Zr-Cu and Ti-Cu based alloys, summarized in **Figure 2** and it was detailed explained by Moon et al. [6]. Theoretically, if the amorphous alloys with high glass-forming ability (GFA), they could be made as the bulk targets by the casting process. According to our previous study, only one case was successful in Zr-Cu-Si system in which the target with a diameter of 127 mm (5 inches) was successfully prepared by a casting process [12]. Since the amorphous materials have been developed with the GFA of the size around 1–2 mm [13], the larger size targets should be prepared by a two-step process; firstly, the alloying powders are prepared by atomization, and then they are consolidated by the proper sintering processes. If the alloying powders could not be prepared by an atomization process as in Mo-Cu [14], Ti-Al [15], and Al-Cr based systems, the proper

**Figure 2.** *Summary of the fabrication of alloying sputtering targets [6].*

ball milling processes were used to prepare the alloying powders. Subsequently, the bulk targets could be made by various sintering processes, such as vacuum hot press (VHP), spark plasma sintering (SPS), hot isostatic pressing (HIP), and so on. The targets could be used without trouble during the sputtering process only when they were consolidated to some specific microstructures with sufficient high toughness [6].
