**About the Editors**

**Braham Prakash** obtained his BSc Engineering Mechanical degree (1974) from Punjab Engineering College Chandigarh and his MTech (Mechanical Engineering) and PhD (Tribology) (1976, 1993) from the Indian Institute of Technology Delhi (India).

He is presently Professor Emeritus at Lulea University of Technology (Sweden) and a Distinguished ˚ Visiting Professor at the Tsinghua University (China). Earlier, he was a Professor and Head of Tribolab at the Division of Machine Elements of Lulea University of Technology (2002–2019), ˚ a faculty at Indian Institute of Technology Delhi (1981–2002) and R&D professional in industry (1976–1981).

He was a Visiting Researcher at Tokyo Institute of Technology (1985) and Fellow of Japan Society for the Promotion of Science (JSPS) at Chiba Institute of Technology (1998–2000). He was Visiting Professor at Tokyo University of Science (2016) as well as at Indian Institute of Technology, Ropar (2010–2013).

His research and teaching activities pertain to high temperature tribology; tribology of materials and lubricants; solid lubricants/self-lubricating coatings; boundary lubrication; tribology of machine components (bearings, gears and seals); analysis of wear problems; and tribotesting.

**Jens Hardell** obtained his MSc degree in Mechanical Engineering in 2005 from Lulea University of ˚ Technology. In 2009, he completed his PhD in Machine Elements at Lulea University of Technology. ˚ He became Associate Professor at the Division of Machine Elements, Lulea University of Technology, ˚ in 2014, as well as Head of Division in 2016.

He was also a visiting Professor at Universite de Lyon, Ecole Nationale d'Ing ´ enieurs de Saint-Etienne ´ in France (2017).

His main research and teaching interests includes high temperature tribology, friction and wear in dry contacts, tribomaterials, surface engineering for friction and wear control, and wear and failure analysis.

## **Preface to "Coatings Tribology"**

Tribological coatings are increasingly used to control (mostly to minimize) friction, wear, and surface damage to move machine components in various applications. The use of coatings, in addition to improving the efficiency and durability of tribological systems, also enables conserving strategic materials and minimize or eliminating the use of hazardous materials. The last few decades have seen massive developments in the field of coatings tribology. A Special Issue of Coatings (ISSN 2079-6412) dealing with various aspects pertaining to coatings tribology was published in 2018. This reprint book is based on this Special Issue and contains 11 research papers dealing with plasma sprayed, ion-beam assisted and sputtered coatings of different compositions. Some of the salient coatings include: NiCr-TiB2 and AlCoCrFeNiTi/Ni60 (plasma sprayed); Cr-Ti.B-N, stainless steel-silver, VCN-Cu, Cu-Al/MoS2, DLC/MoS2 (magnetron sputtered); Ag-MoCo (ion-beam-assisted bombardment); multilayered AlCrN (cathode arc PVD) and polymer composite coatings. The coatings reported in these papers have been deposited on different substrates (including soft substrates) for controlling friction and wear under different operating conditions. The characterization and application aspects of coatings have also been discussed in some of these contributions.

It is hoped that this book will be useful to all those engaged in the control of friction and wear in diverse tribological applications and provide an impetus for further research on this important topic.

The editors would like to take this opportunity to thank MDPI, in particular Ms. Zhiqiao Dong and Ms. Flora Ao for their initiative and support in first bringing out the Special Issue and then this reprint book on coatings tribology.

> **Braham Prakash, Jens Hardell** *Editors*

#### *Article* **Composition versus Wear Behaviour of Air Plasma Sprayed NiCr–TiB 2–ZrB 2 Composite Coating**

#### **Ning Zhang 1, Nannan Zhang 1,\*, Sheng Guan 2, Shumei Li 2, Guangwei Zhang 2 and Yue Zhang 1**


Received: 13 June 2018; Accepted: 5 August 2018; Published: 6 August 2018

**Abstract:** The NiCr–TiB2–ZrB2 composite coating was deposited on the surface of blades made of steel (SUS304) using high-energy ball milling technology and air plasma spraying technology, which aimed to relieve the wear of the blades during operation. The influence of titanium diboride (TiB2) and zirconium diboride (ZrB2) on the microstructure and wear resistance of the coatings was investigated by X-ray diffraction, scanning electron microscopy, Vickers microhardness tester, and a wear tester. The results showed that the TiB2 and ZrB2 particles were unevenly distributed in the coatings and significantly increased the hardness and anti-wear, which contributed to their ultra-high hardness and extremely strong ability to resist deformation. The performance of the coatings was improved with the increase of the number of ceramic phases, while the hardness and wear resistance of the coating could reach their highest value when the TiB2 and ZrB2 respectively took up 15 wt.% of the total mass of the powder.

**Keywords:** TiB2; ZrB2; coating blade; anti-wear
