Mathematical Model of Friction Coefficient Determination for Lubricated Surfaces

This article reviews mathematical model for the determination of friction coefficient for lubricated surfaces which operate works at sliding friction pairs in boundary lubrication case. In the particular model an absolutely smooth ball and rough surface contact is viewed taking into account properties of the material, surface roughness parameters, lubricating material kinematic viscosity and density. The model refers to widely spread ball-on-disc type tribometer where ball is in the contacts with plane

The Influence of the Technological Process on the Surface Quality and Tribological Properties of Powder Details

Nowadays the materials made by methods of powder metallurgy are widely used for producing details of the heavy-duty friction pair. Due to high reliability and effective combination of mechanical and tribological properties such materials are usually used in transport industry, for example for gear assemblies of different kinds of automobiles, brake system of high speed trains, aircrafts etc. There are many variations of powder materials, but for friction pairs the iron based antifriction materials, for example Fe-C-Cu, Fe-P, Fe-Cu-Sn, Fe-Cu-Sn-Pb-MoS2, Fe-C-Cu-Ni-Mo and others are successfully used. In recent years, the requirements for antifriction materials are raised highly because of more intensive freight traffic and speed of vehicles. On the other hand, the demand of more inexpensive materials and effective using of natural resources is the issue of the day.The aim of this paper is to offer the new low-cost metal powder material based on Fe-C compound with content of Ni and Mo up to 0.3%. The influence of the parameters of technological process (pressing and sintering) on physical properties (porosity, density), mechanical properties (hardness) as well as on 2D roughness and 3D texture parameters was studied and is presented in this paper as well. The “Taylor Hobson Ltd” 3D measurement system has been used in metrological study. The analysis of the influence of the technological process on the surface roughness parameters is given. The tribological properties (friction coefficient) were evaluated using “ball-on-disk” testing without lubrication. The analysis of achieved results is prove the appropriateness of using of new low-alloy metal powder material on the iron base for producing details of friction pair. One of the possible applications - bushes for braking systems of railway rolling stock. Using offered material allows reducing the product cost in complex with acceptable wear resistance and durability

Tribological and Mechanical Properties of the Nanostructured Superlattice Coatings with Respect to Surface Texture

This research is funded by the Latvian Council of Science, project “Carbon-rich self-healing multifunctional nanostructured smart coatings (NSC) for high-tech applications using high-power confined plasma technology for their deposition”, project No. 2019/1-0385.Ceramic Nanostructured Superlattice Coatings (NSC) have broad applicability to improve the parts’ and assemblies’ tribological and mechanical properties for the needs of the automotive and aerospace industries. Improving the material properties using nanocoatings for such a widely used material as, for example, bearing steel 100Cr6 makes it possible to improve the service life of machine parts. In this paper, the correlation dependence between tribological and mechanical properties of the NSC and its surface texture are considered to determine how much surface texture will affect the tribological performance of the coated workpieces, as well as the measuring and evaluation procedure of the nanocoatings, are presented. Three different NSC described by a general empirical formula {TiMe1Me2-CN/TiAlSi-N}n and based on the modified carbonitride/nitride non-stoichiometric chemical composition were created, and their tribological and mechanical properties measured and analyzed in the context with surface texture. NSC deposited by the advanced PVD (Physical vapor deposition) technique demonstrated significantly higher wear resistance (up to 28 times), reasonably lower friction coefficient (CoF) (up to 4 times), and significantly higher hardness of the coated workpieces (up to 7 times) versus substrate material. A strong correlation between the steady-state dry sliding friction, CoF, and the amplitude and functional surface texture parameters of tribo-track were observed. The first results of the initiated research regarding the correlation analysis of the tribological and mechanical properties, on the one hand, and surface texture, on the other hand, of the NSC are reported here. © 2022 by the authors.Latvian Council of Science project No. 2019/1-0385; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2