ICMCTF2013 Session E1-2: Friction, Wear, and Lubrication; Effects & Modeling

Tuesday, April 30, 2013 2:10 PM in Room Golden West

Tuesday Afternoon

Time Period TuA Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF2013 Schedule

Start Invited? Item
2:10 PM E1-2-1 Tribology of Hard Carbon Coatings under Ultra- und Super-low Friction Conditions
Volker Weihnacht, Stefan Makowski, Frank Schaller, Andreas Leson (Fraunhofer IWS, Germany)
Hydrogen-free tetrahedral amorp hous carbon (ta-C) films are known to display super-low friction behaviour under boundary lubrication conditions in combination with hydroxyl or carboxyl containing organic lubricants. There is a huge interest to use this effect for technical application in order to reduce friction loss e.g. on engine components or gears and using environmentally friendly lubricants at the same time. Although there are some tribological investigation and first approaches to explain the phenomenon there is still a lack of comprehensive data and understanding of superlubricity behaviour of ta-C. So far it is believed that some kind of a very thin tribochemically reacted friction layer which is formed on the ta-C surface is responsible for the extraordinary low friction. In this contribution a series of tribological investigations with a-C and ta-C coatings, deposited by laser-arc evaporation will be presented. The experiments concentrated on the dependence of lubricant type, sp3-content in the coating, and temperature on the friction and wear behaviour in oscillating sliding wear test. In further experiments, a piston ring on flat configuration with different configurations (coated/uncoated; coated/coated; uncoated/coated) was tested with different lubricants to find out also geometrical influences on tribological behaviour. After the tribological experiments, chemical investigations of mating surfaces in the tribocontact were performed to obtain information on tribofilms and transformation layers.The experimental findings help to get a deeper insight into the superlubricity behaviour of carbon coatings, especially the role of chemical and mechanical effects on friction and wear phenomena.
2:50 PM E1-2-3 Mechanical Properties and Tribological Behavior of a Silica and/or Alumina Coating Prepared by Sol- gel Route on Stainless Steel
Alexis Marsal, Florence Ansart, Viviane Turq, Jean-Pierre Bonino (CIRIMAT, France); JeanMichel Sobrino, Yan-Ming Chen, Julien Garcia (Cetim, France)

The significant development in the mechanical industry requires a constant evolution of skills, particularly in the area of functionalization and protection of metallic alloys surface. The wear of materials is one of the causes of loss of profitability. This study aims to develop solutions to extend the lifetime of stainless steel 316L or 304L whose raw materials are relatively expensive . The main objective in this study is to increase their durabilility by covering these stainless steels with a protecting thin ceramic film. Thanks to their high hardness values, ceramic coatings would present the best properties to fight against wear. Apart from the conventional deposition way such as PVD or CVD, the sol-gel method allows many choices of formulations avoiding a thermal treatment step at very high temperature.

In this work, we have achieved to optimize protective coatings of stainless steel against wear, using sol-gel method associated with dip-coating technique. We have chosen the silica and alumina compounds which are well known as good candidates to tackle this problem because of their intrinsic properties [1,2]. The combination of both oxides is a very promising way for that kind of application even if the literature is not very abundant on these topics. Several synthesis pathways have been investigated to reach this objective. We propose three new routes to achieve this type of coating. First a mixture of sols precursors of both oxides, second with the previous mixture with the incorporation of suspended particles of silica or alumina and the third one corresponding to a single sol precursor of silica or alumina loaded with oxide particles (silica and/or alumina).

This article investigates the various ratios alumina / silica. Processing parameters such as: i) the speed of withdrawal (that controls the coating thickness) and ii) the temperature of the thermal treatment after deposition, have been studied. Structural properties were evaluated by XRD, NMR and Raman. Tribological behavior of the coating was studied in order to select the suitable composition for the targeted application. The friction and the wear between a couple of materials were investigated using a pin on disk standardized test, ASTM G-99.

[1] W. Zhang, Characterization and tribological investigation of SiO2 and La2O3 sol–gel films, Applied Surface Science. 185 (2001) 34-43.

[2] T. Hübert, J. Schwarz, B. Oertel, Sol-gel alumina coatings on stainless steel for wear protection, Journal of Sol-Gel Science and Technology. 38 (2006) 179-184.

3:10 PM E1-2-4 Tribochemically Active Ti-C-S Nanocomposites - a New Concept for Self-lubricating Coatings
Jill Sundberg, Harald Nyberg, Erik Särhammar, Krisztina Kádas (Uppsala University, Sweden); Liping Wang (Lanzhou Institute of Chemical Physics, China); Olle Eriksson, Tomas Nyberg, Staffan Jacobson, Ulf Jansson (Uppsala University, Sweden)

Surfaces that provide low friction as well as mechanical stability are desired in many technical applications. As these two requirements are usually fulfilled by changing material properties in opposite directions, a promising route is to design mechanically stable coatings that are tribochemically active, meaning that they have the ability to become modified by the tribological contact in a way that lowers the friction. A well-known example is nanocomposite coatings such as TiC/a-C, from which carbon can be graphitized to create a lubricating surface layer. Another class of materials is the transition metal dichalcogenides (TMDs), such as WS2 and MoS2. When subjected to the pressure and shear in a tribological contact, the TMD planes become horizontally aligned and thereby enable easy sliding. In the current work, the concept of tribochemically active coatings is applied in a new way by doping TiC/a-C coatings with sulfur, which can be released in the tribological contact to form low-friction compounds.

Coatings were deposited by magnetron sputtering from titanium and carbon targets, with incorporation of sulfur by reactive sputtering using H2S gas. It was found that sulfur goes into the carbide phase, creating a doped TiCxSy phase in a matrix of amorphous carbon. The incorporation of sulfur leads to a lattice expansion of more than 10%. The possibility of release of sulfur was investigated by annealing, which lead to sulfur removal and lattice contraction.

First-principles calculations using supercells and the exact muffin-tin orbitals method were performed for TiCxSy, and the calculated lattice expansions were found to match the experimental ones. Furthermore, the density of states and charge density for TiC and TiCxSy were calculated, showing that the incorporation of sulfur leads to filling of antibonding states and that the sulfur atoms occupy larger volumes than carbon atoms.

Tribological testing against steel balls in an unlubricated pin-on-disk setup showed that increasing sulfur content lead to lower friction and longer lifetimes, an improvement that can be due to changes in microstructure as well as chemistry. However, one of the S-rich coatings was also tested against a W-coated steel ball, leading to a distinct friction reduction (to µ≈0.05). Transmission electron microscopy in the wear track confirmed the local formation of horizontally aligned WS2. It has thus been shown that nanocomposite coatings containing the newly discovered TiCxSy phase are tribochemically active, and offer new possibilities of designing self-lubricating material systems.

3:30 PM E1-2-5 Lubricious Silver Tantalate Films For Extreme Temperature Applications
D'Arcy Stone, Samuel Harbin (Southern Illinois University, US); Hamidreza Mohseni, Jon-Erik Mogonye, Thomas Scharf (University of North Texas, US); Christopher Muratore (Air Force Research Laboratory, Thermal Sciences and Materials Branch, US); Andrey Voevodin (Air Force Research Laboratory, Materials and Manufacturing Directorate, US); Ashley Martini (University of California Merced, US); Samir Aouadi (Southern Illinois University, US)
Silver tantalate was investigated as a potential lubricious material for moving assemblies in high temperature tribological applications. Three different approaches were explored for the creation of such materials on Inconel substrates: (1) powders produced using a solid state method which were burnished on the surface; (2) monolithic silver tantalate thin films deposited by magnetron sputtering; and, (3) an adaptive tantalum nitride/silver nanocomposite sputter-deposited coating that forms a lubricious silver tantalate oxide on its surface when operated at elevated temperatures. Dry sliding wear tests of the coatings against Si3N4 counterfaces revealed friction coefficients in the 0.06 - 0.15 range at T ~ 750 °C. Reduced friction coefficients were found on nanocomposite materials that contained primarily a AgTaO3 phase with a small amount of segregated Ag phase, as suggested by structural characterization using X-Ray diffraction. Furthermore, cross-sectional transmission electron microscopy techniques determined that the reduced friction coefficient at T ~ 750 °C was primarily the result of the formation of a lubricious AgTaO3 phase that reconstructs during the wear process into a mechanically mixed layer of AgTaO3, Ta2O5, and Ag nanoparticles. The presence of nanoparticles of segregated Ag in the thin film further enhanced the performance of these materials by increasing their toughness.
3:50 PM E1-2-6 Lubricious Zinc Titanate Films for High Temperature Applications
Victor Ageh, Hamidreza Mohseni, Thomas Scharf (University of North Texas, US)
This presentation will discuss how defect structure in textured atomic layer deposited (ALD) transition metal oxides films determines friction and wear properties. Specifically this study focuses on the processing-structure-tribological property interrelationships of as-deposited and annealed ALD nanocrystalline zinc titanate (ZnxTiyOz) films. Annealed films at 550°C exhibited improved friction (steady-state friction coefficient of ~0.12) and wear rate (1x10-7 mm3/Nm) compared to the as-deposited films. The ZnTiO3 (104) texture, which is present at temperatures up to 550°C, resulted in improved friction and wear compared to other phases/structures, e.g., Zn2TiO4 cubic spinel structure, annealed at T>550°C. Nanoscale sliding-induced plastic deformation was possible when HRTEM observed ZnTiO3 (104) stacking faults were sheared parallel to the sliding direction resulting in an intrafilm shear velocity accommodation mode. This subsurface aided in shear accommodation (prevented brittle fracture). Since there is predominately (104) slip (i.e., no interacting slips systems), this further translates to low friction and wear. Thus, it is feasible to generate high temperature lubricious oxides through microstructural control at the nanometer level.
4:10 PM E1-2-7 Study of the Friction Coefficient and Wear of Boride Coating Film on Stainless Steel AISI 410 at Different Temperatures
Ernesto García, Marco Figueroa, German Ramírez-Castro, Ivan Campos-Silva (Instituto Politécnico Nacional, Mexico); Stephen Muhl (Universidad Nacional Autónoma de México - Instituto de Investigaciones en Materiales, Mexico); Albano Cavaleiro (University of Coimbra, Portugal); Tomas Polcar (Czech Technical University in Prague, Czech Republic)

In tribological one of the main environment parameters that affect the behavior of the surfaces is the temperature since this can cause surfaces to undergo changes in their mechanical and structural properties. At relative high temperatures, the oxidation layer can affect the tribological characteristics because this is the contact between two surfaces. The oxide layer can reduce or increase the wear rate and the friction coefficient because of a reduction in the contact or the generation of debris. Boriding is a technique used to increase the hardness and the wear resistance of the surface, particularly at high temperatures.

This work presents the results of a study of the tribological performance of a borided layer on the stainless steel AISI 410 at different temperatures under sliding motion wear testing. The borided layer was generated by the package boriding method at 950 °C for 1 hour. X-ray diffraction showed the presence of crystalline CrB, FeB and Fe2B phases. The thickness of the boride layer was 11.9 ± 0.86 μm and the hardness was 24 GPa with a roughness of 120 nm. The sliding tests were performed on a pin on disk tester using an alumina ball counter-body (Al2O3), with an applied load of 1N. The friction coefficient was seen to increase by approximately by 29% with increasing the temperature from Room temperature to 450 °C, with the wear rate showing a similar behavior.

4:30 PM E1-2-8 Plasma Diffusion Treatments to improve the Tribological Performance of Ti-4Al-4Mo-2Sn
Glenn Cassar, Bonnie Attard (University of Malta, Malta); Allan Matthews, Adrian Leyland, John Kavanagh (University of Sheffield, UK)

Ti-4Al-4Mo-2Sn is a high strength, forgeable alpha-beta alloy with good high temperature mechanical properties. This alloy has many potential applications in the aerospace industry, which is currently dominated by the widespread use of Ti-6Al-4V. It is increasingly understood that surface engineering treatments need to be designed for the specific substrate material to be treated (this being particularly important for Ti-alloys) and in this respect no study has yet been carried out for the improvement of the tribological properties of Ti-4Al-4Mo-2Sn by surface engineering means. Triode-plasma oxygen and/or nitrogen diffusion treatments have recently been shown to be extremely effective in reducing surface damage and increasing the wear life of several Ti alloys subjected to dry sliding, abrasion and impact wear.

This work focuses on the development of cost-effective enhanced-plasma processing techniques, which will permit the use of Ti-4Al-4Mo-2Sn in tribological applications – even under relatively high loading. The use of low pressure intensified plasmas (at various temperatures in the range of 600-800 oC) is shown to allow the diffusion of (for example) nitrogen, to generate deep hardened layers. The process parameters for the surface modification technique are selected such as to minimize degradation of mechanical properties and corrosion resistance in the Ti- alloy. The treated specimens were tested and characterized using a variety of techniques, including X-ray diffraction, electrochemical corrosion testing, optical and scanning electron microscopy, nanoindentation, and nanoscratch testing. Furthermore, the effects on the bulk substrate material were also studied by uniaxial tensile and fatigue testing. The results obtained indicate that the proposed technique is capable of significantly improving the tribological characteristics of the chosen Ti alloy without detriment to the substrate microstructure and mechanical properties. The treated surfaces demonstrate improved corrosion behaviour when compared to untreated control samples.

4:50 PM E1-2-9 Tribological Behavior of Pvd Coated Cemented Carbide Against Superduplex Stainless Steel
JoséMarioFernandes Paiva Jr. (Faculdade de Tecnologia SENAI Joinville, Brazil); Ricardo Diego Torres, FredLacerda AMORIM, PauloCesar Soares Jr. (Pontificia Universidade Católica do Paraná, Brazil)

In this work three commercial coatings were tested in a pin on disc setup against UNS S32750super duplex stainless steel. In the first part of this project, adhesion and nano indentation measurements were performed in PVD coated cemented carbide substrates. The pin on disc tests were conducted in a CSM tribometer. The tribological pair consisted of PVD coated cemented carbide and super duplex stainless steel. The adopted load and speed, in the pin on disc tests, were 20N and 20 cm/s, respectively. The pin on disc test was conducted with and without lubrication. The results show that the friction coefficient and wear rate is linked to the coating chemical composition. Moreover, the silicon based coating show the lowest interaction with the stainless steel ball resulting in a low wear rate.

5:10 PM E1-2-10 Influence of the Normal Force and Abrasive Slurry Concentration on the Coefficient of Friction of Thin Films in Micro-abrasive Wear Tests
Bruno Guerreiro, Ronaldo Cozza (Centro Universitário da FEI – Fundação Educacional Inaciana "Padre Sabóia de Medeiros", Brazil)

The purpose of this work is to study the influence of the normal force (N) and abrasive slurry concentration (C) on the coefficient of friction of thin films in micro-abrasive wear tests by rotative ball. Initially, a micro-abrasive wear testing by free rotative ball equipment was designed and constructed, able to measure the coefficient of friction on the tribo-system "thin-film – abrasive slurry – ball". After, experiments were conducted with thin films of TiN, TiC, CrN, TiAlN, HfN, ZrN, TiZrN, TiN/TiAl (multi-layer), TiHfC and TiHfCN, balls of AISI 52100 steel and abrasive slurries prepared with green silicon carbide (SiC) particles + distilled water. All tests were conducted without interruption, and the abrasive slurry was continuously agitated and fed between the ball and specimen. The tangential (T) and normal forces were monitored throughout the tests and the coefficient of friction (μ) was calculated by the equation μ = T/N. The results obtained have shown that:

i) The hardness of the thin films presented influence on the coefficient of friction: high hardness was related with low coefficient of friction;

ii) The coefficient of friction behavior and magnitude were independent of the normal force: for the same thin film and different values of normal force, the coefficient of friction remained, approximately, unchanged;

iii) The concentrations of abrasive slurries affected the magnitude of the coefficient of friction: high abrasive slurry concentration was related with low coefficient of friction.

Time Period TuA Sessions | Abstract Timeline | Topic E Sessions | Time Periods | Topics | ICMCTF2013 Schedule