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Wear particles are produced as a result of interaction of two surfaces in mechanical systems. After extracting and separating particles by different techniques (filtration, ferrography …), their morphology, which is a function of the condition of tribological system (tribosystem), can be related directly to the wear process. In order to understand wear mechanisms, it is interesting to study the relationship between the characterization of wear particles (aspect ratio, shape factor, spike parameter) and the mechanical factors of wear. Therefore, a series of tests were conducted with polytetrafluoroethylene (PTFE) versus cast iron, and flake graphite versus cast iron. Wear particles were studied in a particular tribosystem to understand debris formation and wear. Consequently, after friction tests according to a plane on plane contact, wear particles were collected. After separation tests, particle morphology obtained through image analysis techniques, was used to determine how debris are produced and to elucidate wear mechanisms. Finally, we propose a wear mechanism with these particular tribosystems.

During hot drawing, work tools are subjected to severe constraints. Thus, tool wear is a main preoccupation for industrial engineers. For this reason, it is important to better understand the phenomena which occur at the interface between tool and sheet in this kind of process. That is why, a pin on disc tribometer for high temperature has been designed and achieved. Its originality consists in having an open contact on a continuously new disc surface. This machine permits the simulation of the contact at the tool/product interface during the hot drawing process. In this paper, this new tribometer is described. Then, a friction and wear comparative study of various tool materials is carried out at a temperature of 400 °C and with a pressure of 20 MPa. The classification of these materials is done according to the measurement of the friction coefficient and the wear characterization. Pins, which represent tools are: X153CrMoV12 steel samples uncoated and coated with TiAlN deposited by PVD process and nodular cast iron GJS 600 ones. Sheets made of steel and representing drawing products are: uncoated and coated samples by bimetallic alloy coating. The tribometer is able to classify and to evaluate the tribological performances of the different combinations of pins and sheets. Tests show that coatings reduce friction. However, they do not prevent adhesive wear of pins.

The total replacement of damaged or diseased synovial joints represents one of the greatest advances in orthopaedic surgery of the 20th century. Whereas replacements are available for the shoulder, ankle, elbow, and knee, hip accounts particularly for the most surgical interventions. In France, 100,000 hip joints per year are replaced and all the implants consist of a sliding pair represented by a hard counter face, either metal or ceramic, and commonly a softer polymer. Ultra high molecular weight polyethylene (UHMWPE) was first used in joint replacement in the early 1960s. Since that time, it had been the dominant polymer for bearing surfaces in orthopaedic surgery. However, generation of UHMPWE wear debris from bearing surfaces in patients is the major problem for long term implants. Both volume and morphology of the wear particles determine the response of the body to debris, and subsequent effects on secure fixing. This paper presents a review of the type of particles most frequently found in biopsies of tissues from explanted prostheses. Indeed, the size and the amount of these debris are very important factors for a better understanding of wear and corrosion wear processes in artificial joints. Real wear particles are also described in this paper.

Le procede d'emboutissage a chaud avec trempe dans les outils est un procede de mise en forme recent specialement destine a une classe particuliere de toles en acier trempable et aluminie. L'usure des outils lors de ce procede est une preoccupation importante dans l'industrie. C'est dans cette optique qu'un nouveau tribometre pion sur disque a haute temperature a ete concu et realise pour simuler les conditions de contact a l'interface outil/tole. Une etude tribologique a chaud a ete menee sur des materiaux a outils utilises dans ce procede. Les pions, qui representent l'outil sont en acier X153CrMoV12 revetu par du TiAlN depose par PVD et en acier non revetu. Les toles (produits d'emboutissage) sont des toles revetues par une couche alliee aluminium – silicium. Les performances de ces materiaux ont pu etre quantifiees par la mesure du coefficient de frottement et la caracterisation de l'usure. Les essais effectues montrent que le revetement TiAlN augmente le frottement. De plus, il ne protege pas les pions contre l'usure adhesive.

The aim of this article is to find correlations between the characteristics of the wear particles, the coefficients of friction and the wear rates in order to determine wear mechanisms. In the air compressors, piston rings are made of polytetrafluoroethylene (PTFE) but its wear rate is very high and it must be reinforced. This work is devoted to the influence of temperature with three types of PTFE (pure and filled with glass fibre and carbographite) against flake grey cast iron thanks to a phenomenological study of the contact.

Surface treatments and coatings are the practical approaches used to extend the lifetime of components and structures especially when the surface is the most solicited part of the considered engineering component. Hard thermally sprayed coating is one of the most wear resistance coating widely used in many practical mechanical applications. In the construction of articulating parts of medical devices, titanium and its alloys have to be surface coated to improve their tribocorrosion behavior. In this way, the use of porous thermal coatings is known to be a strategy for better binding bone or tissue on femoral stem for example. It is, thus, important to evaluate the corrosion and the wear behaviors of such materials for biosecurity considerations in the human body. In this study, we investigate the behavior of new nano ZrO2 and Al2O3-13 wt.% TiO2 thermal sprayed coatings on commercially pure (cp)-Ti (grade 4) and titanium alloy substrates. Friction and wear tests against Al2O3 balls showed that the wear resistance of Al2O3-13 wt.% TiO2 is better than that ZrO2 coating. Both plasma sprayings have similar abrasive wear behavior; however, the average friction coefficient is higher for alumina–titania coating. Electrochemical tests, open circuit potential monitoring and potentiodynamic polarization, were performed in simulated body conditions (Hank’s solution, 37 °C). Results showed that corrosion resistance was appreciably higher for alumina–titania coating.

Les lubrifiants jouent un role important dans la protection des outils et produits de mise en forme. Ceci est particulierement vrai dans le cas du laminage a chaud. Dans ce procede, les lubrifiants sont soumis a des sollicitations thermiques et mecaniques severes. Pour repondre a ces exigences, des additifs speciaux leur sont rajoutes. Dans ce contexte, nous avons realise des essais avec differents types de lubrifiants sur un tribometre a haute temperature en contact lineique galet/plan. Ces essais mecaniques ont ete completes par une serie d’analyses physiques et chimiques de ces lubrifiants afin de relier leur comportement mecanique a leur composition. Suite aux differents resultats obtenus, nous avons reussi a trouver des correlations. Ainsi, les huiles synthetiques donnent le coefficient de frottement, µ, le plus bas (0,12 environ) et une usure douce des facies des pistes. En effet, elles contiennent notamment des esters (reducteurs de frottement) ainsi que plusieurs types d’additifs. Quant a l’huile d’origine vegetale, qui contient une grande quantite d’esters, elle donne des resultats sensiblement comparables a ceux des huiles synthetiques (µ = 0,14). Enfin, les huiles minerales, qui ne contiennent pas d’additifs, donnent les resultats les plus mauvais en terme de coefficient de frottement (µ = 0,28) et d’usure de piste.