Effect of Negative Bias Voltage on Tribological Properties under High Relative Humidity Environment and Corrosion Resistance of Boron Carbide Coatings

Ping Zhong,Xueqian Cao,Lunlin Shang

doi:10.3390/met11101518

Ping Zhong, Xueqian Cao + Show 1 more

Open Access

https://doi.org/10.3390/met11101518

Copy DOI

Abstract

Humid air is a very important service environment, in which metal friction parts should be enhanced to offer excellent corrosion resistance and wear resistance. The B4C coating is an excellent candidate material to enhance the corrosion resistance and tribological behaviors. The purpose is to investigate the effect of negative bias voltages on the tribological properties of B4C coatings under a high relative humidity environment. Amorphous B4C coatings were successfully prepared by closed field unbalanced magnetron sputtering technology and its microstructure, hardness, elastic modulus, adhesive force and tribological properties were systematically studied. Results demonstrate that the B4C coatings deposited at each negative bias voltage have a columnar structure and the surface roughness remained unchanged (about 1.0 nm), while the thickness, hardness, elastic modulus and adhesion force increase first and then decrease with the negative bias voltage increasing. Among them, the B4C (−50 V) coating showed the best mechanical properties. It should be noted that the B4C (−50 V) coating with an excellent corrosion resistance also exhibits the lowest friction coefficient (~0.15) and wear resistance (7.2 × 10−7 mm3·N−1·m−1) under humid air (85% RH). This is mainly due to the tribochemical reaction of B4C during a sliding process to produce boric acid at the sliding interface. B4C coatings can provide an excellent corrosion resistance and high wear resistance due to their high chemical stability and high hardness.

Highlights

Metal friction pairs face various atmosphere environments during service, such as high temperature, methane, dry nitrogen, dry air and humid air [1,2,3,4]
The development of magnetron sputtering sources over recent years has attracted extensive attention to the B4C coating deposited by closed field unbalanced magnetron sputtering technology [11,12,13,14]
B4C coatings with different properties were successfully deposited on the substrate by adjusting the negative bias voltage (0 V, −50 V, −100 V, −150 V)

Summary

Introduction

Metal friction pairs face various atmosphere environments during service, such as high temperature, methane, dry nitrogen, dry air and humid air [1,2,3,4]. Humid air is a very important service environment, and the surface of metal friction parts should be modified to have a high hardness and high chemical inertness in order to offer an excellent corrosion resistance and wear resistance. The prepared B4C coatings by closed field unbalanced magnetron sputtering technology have excellent physical and chemical properties, such as excellent mechanical properties, a high adhesion, uniform and compact surface and small roughness [7]. B4C coatings were prepared by unbalanced closed field magnetron sputtering equipment, and the effects of negative bias voltage on the cross-section and surface morphology, thickness, microstructure and bonding strength of B4C coatings were systematically investigated. The results of this paper have an important guiding significance for the deposition of B4C coatings with excellent mechanical properties, low friction and high wear resistance by closed field unbalanced magnetron sputtering technology

Materials and Methods

Tribological Performances and Corrosion Resistance of B4C Coatings

Findings

Conclusions