The purpose of the study is to evaluate the cutting performances of tool material CBN 7050 produced during turning bearing steel 100Cr6 soaked. Tests of tools' wear of long life were carried out. The method adopted for the realization of these tests is that of the experimental designs. A mathematical models validated by the criterion of Fisher, allow to predict the lifetime T of the tested tool material, and the expected roughness Ra (surface integrity). They are necessary for optimization and the industrial exploitation. The roughness Ra was taken as the same moment as the wear Vb. The experimental results have a better output in terms of lifetime (T = 62.94 min.), and surfaces roughness (Ra = 0.25 to 1.01 μm) to Vc = 120 m/min. (cutting speed) include in borders for those of the grinding. Non linear optimization of the lifetime material (CBN 7050) under the surface state (Ra) taken as inequality constraint to Matlab mean allows to release an optimum (T = 61.73 min.) to Vc_opt = 120 m/min. near to the experimental value with 98%.

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Electrically conductive tribo-coatings (i.e. Ir-DLCs) were developed using a hybrid deposition process, combining RF-PECVD with DC magnetron sputtering of Ir. Pin-on-plate tribotests in reciprocating motion were performed in air on Ir, DLC and Ir-DLC coated plates against bearing steel pins under 0.5 N load. The electrical contact resistance was measured during the tribotests, and for Ir-DLC it was below 30 Ω. Neither the pure DLC layer nor the pure Ir layer reached friction coefficients lower than 0.2, while the Ir-DLC went down to 0.05. For Ir-DLCs, however, relatively high and unstable friction was occasionally observed. Possible causes of the instability are discussed by focusing on the characteristics of the tribofilm and the formation of wear debris.

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The objective of this research is to investigate the frictional behavior of a-C:H coating in plane contact by using reciprocating micro-sliding test under controlled relative humidity. The friction tests were conducted at various relative humidities (RH) between 5% and 90% without lubrication at room temperature under the following conditions: normal load of 1 N, sliding stroke of 2 μm, sliding speed of 10 μm/s, and up to 80000 cycles. The friction coefficient of the DLC coatings first increased and then decreased with increasing relative humidity when the number of sliding cycles was below 30000. Critical relative humidity was noticed, which corresponded to the highest coefficient of friction. At a relative humidity of 80%, the friction coefficient became almost constant over the whole number of sliding cycles.

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Under the elliptical contact conditions with an ellipticity parameter of K_e=1.4, a non-Newtonian thermal EHL analysis was carried out. The lubricating oil was assumed to behave as a Maxwell fluid. Lubricating oil is the automotive traction oil with the viscosity grade of ISO VG32. Input parameters are maximum Hertzian pressure P_H=1.5 GPa, entrainment velocity u_e=10 m/s, slide-roll ratio Σ=0%∼4.0% and inlet oil temperature t₀=413 K. The shear stress distribution under elliptical contact conditions showed a similar tendency to that obtained in point contact conditions, and it was found that the traction coefficients at maximum Hertzian pressure of P_H=1.5 GPa are scarcely affected by the shape of contact area. Furthermore, although both the pressure distributions and the temperature distributions hardly changed up to the slide-roll ratio of Σ=1.0%, the considerable variation in the shear stress distributions was recognized.

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Calcium-di-2-ethylhexyldithiophosphate (CaDTP) was synthesized and its lubricating properties were compared with those of zinc-di-2-ethylhexyldithiophosphate (ZnDTP) and chlorinated pentadecane (CP). CaDTP was similar to and better than ZnDTP regarding anti-wear property and load-carrying capacity in a high speed four-ball tester. CaDTP also performed as good as CP and better than ZnDTP in cutting and forming tests. The results suggest that the lubricating mechanism of CaDTP may be slightly different from that of ZnDTP and calcium atoms play an important role in the performances of the compound.

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