On the Microstructure and Mechanical Properties of CrNx/Ag Multilayer Films Prepared by Magnetron Sputtering.

Chunfu Hong,Jianbo Wu,Pingshan Zhang,Fa Chang,Ping He,Jun Tian,Pinqiang Dai

doi:10.3390/ma13061316

Abstract

CrNx/Ag multilayer coatings and a comparative CrNx single layer were deposited via reactive magnetron sputtering. In multilayer coatings, the thickness of each CrNx layer was constant at 60 nm, while that of the Ag layer was adjusted from 3 to 10 nm. Microstructure of the films was characterized by X-ray diffraction and transmission electron spectroscopy. The results suggest that the film containing 3 nm of Ag layer presents a nanocomposite structure comprising fine nano-grains and quasi-amorphous clusters. With Ag layer thickness reaching 4.5 nm and above, Ag grains coalesce to produce continuous an Ag layer and exhibit (111) preferential crystallization. Hardness of the films was detected by nanoindentation and it reveals that with increasing the Ag layer thickness, the hardness continuously decreases from 30.2 to 11.6 GPa. Wear performance of the films was examined by the ball-on-disk test at 500 °C. The result suggests that the out-diffusion of Ag towards film surface contributes to the friction reduction, while the wear performance of films depends on the thickness of the Ag layer.

Highlights

In recent years, with increasing demands of low friction contact or dry machining at elevated temperature, coatings combining phases of hard nitride and solid lubrication have been extensively studied [1,2,3,4,5]
The aim of this paper is to study the relationships between the microstructure and mechanical properties in CrNx /Ag multilayer films
CrNx single layer and CrNx /Ag multilayer films were deposited by reactive magnetron sputtering in Ar/N2 atmosphere

Summary

Introduction

With increasing demands of low friction contact or dry machining at elevated temperature, coatings combining phases of hard nitride and solid lubrication have been extensively studied [1,2,3,4,5]. Ag is a soft metal that provides low friction against hard surfaces at temperatures ranging from room temperature (RT) to 700 ◦ C, and becomes a good self-lubricating component combining with the nitride phase. H. Köstenbauer et al reported that magnetron sputtered TiN/Ag nanocomposite films possessed lower friction coefficient than monolithic TiN. Köstenbauer et al reported that magnetron sputtered TiN/Ag nanocomposite films possessed lower friction coefficient than monolithic TiN They suggested a critical Ag content was required to activate the segregation of Ag towards the film surface and to reduce the friction coefficient and wear loss at higher temperature [7]. Mulligan et al reported the friction and wear behavior of CrN/Ag nanocomposite films with regard to the film content, microstructure and temperature effects [8,9,10,11,12]

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