Low Friction CrNMPP/TiNDCMS Multilayer Coatings.

J Paulitsch,C Maringer,P H Mayrhofer

doi:10.1007/s11249-012-9922-y

Abstract

Transition metal nitrides like CrN and TiN are widely used in automotive applications due to their high hardness and wear resistance. Recently, we showed that a multilayer architecture of CrN and TiN, deposited using the hybrid—high power impulse magnetron sputtering (HIPIMS) and direct current magnetron sputtering (DCMS)—HIPIMS/DCMS deposition technique, results in coatings which indicate not only increased mechanical and tribological properties but also friction coefficients in the range of diamond-like-carbon coatings when tested at RT and ambient air conditions. The modulated pulsed power (MPP) deposition technique was used to replace the HIPIMS powered cathode within this study to allow for a higher deposition rate, which is based on the complex MPP pulse configuration. Our results on MPP/DCMS deposited CrN/TiN multilayer coatings indicate excellent mechanical and tribological properties, comparable to those obtained for HIPIMS/DCMS. Hardness values are around 25 GPa with wear rates in the range of 2 × 10−16 Nm/m3 and a coefficient of friction around 0.05 when preparing a superlattice structure. The low friction values can directly be correlated to the relative humidity in the ambient air during dry sliding testing. A minimum relative humidity of 13% is necessary to guarantee such low friction values, as confirmed by repeated tests, which are even obtained after vacuum annealing to 700 °C. Our results demonstrate that the co-sputtering of high metal ion sputtering techniques and conventional DC sputtering opens a new field of applications for CrN/TiN coatings as high wear resistance and low friction coatings.

Highlights

Chromium and titanium nitride (CrN, TiN) thin films are the focus on many research activities as they are ideal candidates to study the interrelation between microstructure, morphology and resulting properties [1,2,3,4]
We showed that a multilayer architecture of CrN and TiN, deposited using the hybrid—high power impulse magnetron sputtering (HIPIMS) and direct current magnetron sputtering (DCMS)— HIPIMS/DCMS deposition technique, results in coatings which indicate increased mechanical and tribological properties and friction coefficients in the range of diamond-like-carbon coatings when tested at RT and ambient air conditions
The modulated pulsed power (MPP) deposition technique was used to replace the HIPIMS powered cathode within this study to allow for a higher deposition rate, which is based on the complex MPP pulse configuration

Summary

Introduction

Chromium and titanium nitride (CrN, TiN) thin films are the focus on many research activities as they are ideal candidates to study the interrelation between microstructure, morphology and resulting properties [1,2,3,4]. Coatings prepared by arc evaporation are in general characterized by very dense morphologies, due to the high ionization rate and available energies, but often exhibit a high density of macro particles (droplets) ejected from the cathode [5, 6]. As an alternative to HIPIMS the modulated pulsed power (MPP) technique has been developed, exhibiting longer pulse durations, ranging from 400 to 3,000 ls, as well as multiple steps and micro pulses within a single pulse [19,20,21] Due to this approach, low and high density discharges during one long pulse can be achieved resulting in typical maximum target power densities up to 0.5 kW/cm2 [21]. In agreement to previous results, the prepared CrNMPP/TiNDCMS exhibit friction coefficients of *0.1, as well as the same dependence to the different ambient atmosphere used during testing

Experimental

Results and Discussion

Summary and Conclusion