Effects of annealing treatment on tribological behavior of tungsten-doped diamond-like carbon film under lubrication (Part 2): Tribological behavior under MoDTC lubrication

Shaojun Zhang,Yanyan Wang,Jiajie Kang,Haidou Wang,Lina Zhu,Haipeng Huang,Guang’An Zhang,Guozheng Ma,Wen Yue

doi:10.1007/s40544-021-0514-4

Abstract

Molybdenum dialkyldithiocarbamate (MoDTC) is widely used as a friction modifier in engine lubricating oil. Under MoDTC lubrication, the friction and wear behaviors of tungsten-doped diamond-like carbon (W-DLC) films annealed at 100–400 °C were discussed and evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy. Under (polymerized alpha olefin) PAO + MoDTC lubrication, the coefficient of friction of all samples decreased, but the wear rates of the W-DLC films annealed at 300 °C increased significantly. By interacting with zinc dialkyldithiophosphate (ZDDP), the wear rates of W-DLC films annealed at different temperatures declined significantly owing to the formation of dense phosphate tribofilms on the worn surfaces.

Highlights

The efficiency and life of the engine affects its energy saving and economic performance
The interactions between annealed wear behaviors of tungsten-doped diamond-like carbon (W-Diamond-like carbon (DLC)) films, Molybdenum dialkyldithiocarbamate (MoDTC), and MoDTC + zinc dialkyldithiophosphate (ZDDP) were studied, and the main conclusions are as follows: 1) Under PAO + MoDTC lubrication, MoS2 and WO3 were produced on the W-DLC film surfaces owing to the addition of MoDTC, which led to a decrease in coefficient of friction (COF)
The COF of W-DLC films annealed at 100–300 °C was lower than that of the unannealed samples, whereas the intensity of the C–C bond Raman peak of the former was higher than that of the latter

Summary

Introduction

The efficiency and life of the engine affects its energy saving and economic performance. Diamond-like carbon (DLC) films are widely used in engine systems owing to their high hardness, good lubrication performance, and chemical inertness [1,2,3,4]. DLC films are metastable amorphous structures composed of sp and sp carbon bonds (sp2-C and sp3-C). The conversion from sp3-C into sp2-C occurs at high temperatures, resulting in a change in the structure and properties of DLC films [5,6,7,8]. The working temperature of the engine is 120–150 °C [9, 10]. The flash temperature during the friction process may reach 200 °C, which is an important factor for increasing the temperature of the working surface [11, 12]

Results

Discussion

Conclusion