DLC coated spur gears – Part II: coating properties and potential for industrial use

Purpose This paper aims to address the coating and compound analysis of diamond-like carbon (DLC) on steel, to understand the frictional behavior in tribological gear systems presented in paper Part I. Here, the Ti and Zr modified DLC coating architectures are analyzed regarding their chemical, mechanical and thermophysical properties. The results represent a systematic analysis of the thermal insulating effect in tribological contact of DLC coated gears. Design/methodology/approach The approach was to evaluate the effect of the substitution of Zr through Ti at the reference coating ZrCg to TiCg and the effect on thermophysical properties. Furthermore, the influence of different carbon and hydrogen contents on the coating and compound properties was analyzed. Therefore, different discrete Ti or Zr containing DLC coatings were deposited on an industrial coating machine. Thereby the understanding of the microstructure and chemical composition of the reference coatings is increased. Findings Results prove comparable mechanical properties of metal modified DLC independent of differences in chemical compositions. Moreover, the compound adhesion between TiC g /16MnCr5E was improved compared to ZrC g /16MnCr5E. The effect of hydrogen content Ψ and carbon content x c on the thermophysical properties is limited by Ψ = 18 at.% and x c = 90 at.%. Practical implications The findings of the combined papers Part I and II show a high potential for industrial application of DLC on gears. Based on the results DLC coatings and gears can be tailored to each other. Originality/value Systematic analysis of DLC coatings were conducted to evaluate the effect of titanium, carbon and hydrogen on thermophysical properties.