Lubricious TiSi(V)N coatings for extreme temperature application deposited by Deep Oscillation Magnetron Sputtering (DOMS) mode

Development of new self-lubricant coating systems with control of the lubricous species diffusion have enormous potential to be used in the protection of surfaces in components for machining. In the last years, vanadium rich coatings have been introduced as possible candidates for self-lubrication due to their optimum tribological properties. This work is devoted on the study of V additions on the morphology, structure and on the tribological properties of TiSiN films deposited by HiPIMS in Deep Oscillation Magnetron Sputtering (DOMS) mode. Two different peak powers were used on the deposition of coatings in order to produce films with different morphology. The tribological properties of coatings were evaluated at room temperature against Al2O3 balls on a pin-on-disc apparatus. Increasing of peak power showed to change the cross section morphology of films from columnar type to compact structure. V additions improved the tribological properties of TiSiN coatings.This research is sponsored by FEDER funds through the program COMPETE – Programa Operacional Factores de Competitividade – and by national funds through FCT – Fundação para a Ciência e a Tecnologia, under the projects: PTDC/EMETME/ 122116/2010 and PTDC/EMS-TEC/1805/2012. The authors acknowledge the Master student Melkamu A. Mekicha (co-author of this paper) from the International Joint European Master in Tribology of Surfaces and Interfaces (TRIBOS) program, doing his thesis in the mechanical engineering department of the University of Coimbra, for his special dedication on the development of this research

The effect of hard chrome plating on iron fines formation

Scratch tests and reciprocating sliding tests were carried out under lubricated conditions to explore the influence of hard chrome plating on iron fines formation. In the scratch tests, the effect of hard chrome plating on iron fines formation at single asperity contact due to its inherent property have been investigated. In the reciprocating sliding tests, the initial roughness of the substrate and the roughness changes introduced due to the hard chrome coating have been taken into account. It was found that both the tribochemistry of the chromium layer and the smoothening of aggressive roughness features from the grinding process due to chrome plating play an important role in reducing iron fines formation

Study of wear particles formation at single asperity contact: An experimental and numerical approach

Wear particles generated due to the relative sliding of the roll and the sheet metal in the roll bite are one of the main factors that contaminate the surface of a cold rolled steel sheet. The details of the wear mechanisms in the contact of individual roll-sheet asperities define the total amount of wear particles generated. In this paper, a micro-mechanical experimental approach is coupled with material point method (MPM) scratch simulations to study the friction and wear behavior of a single roll asperity sliding through a sheet metal. Micro-tribology experiments in the form of single asperity scratch testing showed that ploughing is the dominant wear mechanism in lubricated conditions, while wedge forming was the main wear mechanism in the absence of lubricant. The beneficial influence of chrome plating the rolls on wear particles formation is found to stem from its interaction with the lubricant as the same influence was not observed in non-lubricated test conditions. MPM single asperity simulations revealed that almost all the frictional resistance arises from deforming the substrate in the case of an interfacial shear strength corresponding to the lubricated contact. In contrast, MPM showed that, in unlubricated sliding, the frictional resistance is primarily due to shearing of the adhesion junction and tearing the deforming body. Furthermore, using the degree of wear of the scratch experiments as a benchmark, a critical plastic strain needed to produce wear particles was found to be between 3 to 4 for the investigated interstitial-free steel