A METHOD FOR THE ASSESSMENT OF THE ROLLING CONTACT FATIGUE OF MODERN ENGINEERING MATERIALS IN LUBRICATED CONTACT

It is widely recognised that apart from scuffing, rolling contact fatigue (RCF) is one of the most predominant failure types in highly loaded non-conformal friction joints. The fatigue life of machine parts depends on many factors that can be divided into three groups: design, technology and operating conditions. The main factors influencing pitting are material properties, the geometry of the tribosystem, surface finish, dimensional precision, and working conditions as well as the physicochemical properties of the lubricant. The aim of this paper is to present the experimental method for determining fatigue life of modern engineering materials in lubricated rolling contact. The developed method allows an investigation into the effect of all these factors on rolling contact fatigue (pitting). The method is employed by using a modified four-ball testing machine denoted as T-03. The modification embraces the replacement of testing specimens. The upper ball is replaced with a cone that can be made of various materials. The method exhibits good resolution and is time and cost effective. It was successfully applied to the investigation into various types of surface coatings including single, multilayer and duplex coatings. This method can be employed by using a widespread four-ball apparatus

A METHOD FOR THE ASSESSMENT OF THE ROLLING CONTACT FATIGUE OF MODERN ENGINEERING MATERIALS IN LUBRICATED CONTACT

It is widely recognised that apart from scuffing, rolling contact fatigue (RCF) is one of the most predominant failure types in highly loaded non-conformal friction joints. The fatigue life of machine parts depends on many factors that can be divided into three groups: design, technology and operating conditions. The main factors influencing pitting are material properties, the geometry of the tribosystem, surface finish, dimensional precision, and working conditions as well as the physicochemical properties of the lubricant. The aim of this paper is to present the experimental method for determining fatigue life of modern engineering materials in lubricated rolling contact. The developed method allows an investigation into the effect of all these factors on rolling contact fatigue (pitting). The method is employed by using a modified four-ball testing machine denoted as T-03. The modification embraces the replacement of testing specimens. The upper ball is replaced with a cone that can be made of various materials. The method exhibits good resolution and is time and cost effective. It was successfully applied to the investigation into various types of surface coatings including single, multilayer and duplex coatings. This method can be employed by using a widespread four-ball apparatus

The analysis of measurement data collection systems from the tribotesters

When conducting tribological model studies with the aim of achieving a high repeatability and reproducibility of results, much attention is paid to the precise setting of test parameters. Most of all, setting the sliding speed and normal load is made with great care. Ambient conditions (temperature, humidity) are also controlled. At the same time, issues related to inaccuracy in making samples are often marginalized. Inaccuracies in surface geometric texture and shape are often caused by additional technological processes carried out after a precise execution of the sample base. This often increases the axial and radial run-out of samples. Moreover, it may lead to a misinterpretation of the measurement of linear wear intensity and friction. In order to eliminate the impact of the axial run-out on the measurement of linear wear intensity, the authors have developed a concept as well as designed and built an automated computer-controlled system of triggering the measurement of tribological characteristics as a function of a disc position, which is no longer as a function of time. This system was applied in the system of the T-01M produced by ITeE – PIB Radom. The modified system was tested on two types of material combinations and with a high variability of the speed of the node. In addition, the results of tribological characteristics obtained with a standard measuring system triggered with time were compared with those obtained using the developed system. The study shows that the use of an automated system of triggering measurement as a function of a disc position enables a considerable decrease in scattering measurement results at low engine speeds, thereby improving repeatability and reproducibility of tribological studies in the system ball-on-disc and pin-on-disc

Testing of the Resistance to Scuffing of Spiral Bevel Gears: Test Rig, Method, and Results of Verification Testing

In spite of long-term development of the technology of bevel gear production, the automotive industry reports various operational demands such as the need of the size and mass reduction of gears without lowering their durability and reduction of friction leading to a decrease in the energy losses and a decrease of the tendency to scuffing. What is more expected, EU regulations may impose the use of new generation gear oils (ecological-friendly) providing the proper operational properties of the transmission. In view of these demands, a new, bevel gear test rig and scuffing test method have been developed at ITeE-PIB. The idea resulted from a necessity to improve reliability of tests—popular gear tests are run mostly on spur gears having the tooth geometry significantly different than bevel gears. The test rig, test method, and results of verification testing are presented. The effect of various gear oils and the deposition of a low-friction coating on the resistance to scuffing were investigated. It is shown that the new test rig fulfils the research requirements and that the new test method has a good resolution

Wpływ dodatku grafenowego na właściwości tribologiczne bionicznych kompozycji smarowych testowanych metodą SRV

The aim of the study was to investigate the effect of the addition of graphene dispersion on anti-wear properties of bionic lubricant compositions based on aqueous sodium hyaluronate solutions. Tribological tests were carried out using a SRV tester, enabling the tests to be carried out in conditions of linear oscillating movement of the bullet-shield type association in which the ball was made of aluminium oxide and the disc was made of bearing steel 100Cr6. For research, a 0.5% solution of sodium hyaluronate in water (composition BSS2) was chosen, which was the base to which the graphene additive was introduced. During the main stage of work, three lubricant compositions were tested, i.e., as well as BSS2 solution, into which 0.05% m/m or 0.1% m/m graphene oxide was introduced, respectively. The study allowed the observation of a clear anti-wear effect associated with the introduction of graphene preparations into the hyaluronan base, manifested in a change in the trend of the graph of the coefficient of friction over time. In addition, a reduction in the volume wear of friction node components was found. Based on the analysis of tribological research results, it was found that the anti-wear effect of the lubricant on the friction elements of the steel-ceramic material combination increases with increasing the content of the graphene preparation in the lubricant composition.Celem pracy było zbadanie wpływu dodatku dyspersji grafenowej na właściwości przeciwzużyciowe bionicznych kompozycji smarowych na bazie wodnych roztworów hialuronianu sodu. Badania tribologiczne przeprowadzono, stosując tester SRV, umożliwiający realizację testów w warunkach liniowego ruchu oscylacyjnego skojarzenia typu kula–tarcza, w którym kula wykonana była z tlenku aluminium, a tarcza ze stali łożyskowej 100Cr6. Do badań wybrano 0,5-procentowy roztwór hialuronianu sodu w wodzie (kompozycja BSS2), stanowiący bazę, do której wprowadzano dodatek grafenowy. Podczas zasadniczego etapu prac testowano trzy kompozycje smarowe, tj., kompozycję BSS2, a także roztwór BSS2, do którego wprowadzono odpowiednio 0,05% m/m lub 0,1% m/m tlenku grafenu. Przeprowadzone badania pozwoliły na zaobserwowanie wyraźnego efektu przeciwzużyciowego związanego z wprowadzeniem preparatów grafenu do bazy wodno-hialuronianowej, przejawiającego się zmianą trendu wykresu zależności współczynnika tarcia w czasie. Ponadto stwierdzono redukcję zużycia objętościowego elementów węzła tarcia. Na podstawie analizy wyników badań tribologicznych stwierdzono, iż efekt przeciwzużyciowego oddziaływania substancji smarowej na elementy trące skojarzenia materiałowego stal–ceramika wzrasta wraz z podwyższaniem zawartości preparatu grafenowego w kompozycji smarowej

IJTC2007-44244 THE PROBLEMS OF APPLICATION OF PVD/CVD THIN HARD COATINGS FOR HEAVY-LOADED MACHINE COMPONENTS

ABSTRACT The authors developed test methods for investigation of heavy-loaded coated machine elements: scuffing and pitting. Results of their investigation indicate the very positive role of coatings for increasing resistance to scuffing. The authors stated that the role of usually toxic lubricating additives can be taken over by the thin coating. The crucial problem is pitting. Comprehensive research indicates that steel components with typical PVD coatings (eg. TiN, CrN) usually do not exhibit a satisfactory fatigue life. However the results of experiments performed by the authors for new coatings are encouraging. INTRODUCTION The development of transmissions and bearings is characterized by continuously increasing levels of torque and power, increased service life, improved efficiency and stringent noise requirements. Over recent years, the opportunities provided by conventional technologies to increase performance have been exploited. The breakthrough technologies for heavyloaded steel parts are thin hard coatings. At present, thin hard coatings are commonly used on cutting and forging tools (nearly 80% cutting tools and over 40% forging tools are coated). The proportion of mechanical components that are coated is extremely small (less than 2 %). The description of the pitting wear is summarized i