Proceedings of SerbiaTrib '13

comes to the sharp increase of wear rate and toreduction of pressure. Lubrication with synthetic oilhas a smaller increase of wear rate and smallerreduction of pressure.Based on the foregoing analysis, it can beconcluded that the Hertzian contact stress dependson the choice of lubricant. Synthetic lubricating oilis the most favourable from the aspect of wear, andin terms of achieving hydrodynamic lubrication.Optimal lubrication conditions were obtained forthe rotation speed of n 1 = 5000 min -1 or slidingvelocity v gs = 2.53 m/s.6. DAMAGE TYPES6.1. WearFigure 4. Wear on wheel tooth surface withoutadditional treatment for T 2 = 36 Nm; t = 260 h;n 1 = 5000 min -1tribological system are: the gear wheel (basicbody), the worm (opposed body) and the lubricant(intermediate component).Experiments with wheels with differentadditional treatments provide basic knowledge ofsintered gears load capacity. Worm and wheel arein contact in a point. During operation, a change inthe tooth flank of the wheel appears due to wear.The worm forms on the tooth flank of the wheel, awear surface that has a shape that is identical toworm gear flank. Wear progress widens the wearsurface, which leads to a lower Hertzian pressure inthe tooth contact. After a certain period of operationunder intensive wear progress, the steady stateoccurs, where a necessary oil layer exists, so thatthe wear progress is minimal. Figure 4 shows theform of wear damage on tooth surface of wheelmade from material without additional treatment.Figure 5 compares all experiments with wheelsof different material variants after a trial of 100 hand an output torque of 20 Nm. The maximumwear, δ wn = 115 m, occurred on material S2 –material with case hardening. The minimum wear,δ wn = 7.8 m, occurred on S5 – sinter-hardening.Figure 4 shows the wear width of the wear surfaceon wheel from material S4 - “pyrohydrolysis” andS5 sinter-hardening for different speeds. TheFigure 5. Wear δ wn for all trials with different material variants [6]The wear describes the continuous loss ofmaterial from the surface of the basic body whichhas a relative movement with respect to a solid,liquid or gaseous mating with which it is in contact[7]. Wear has exclusively mechanical causes.Different from hardness or tensile strength, wear isnot a specific material property but a systemproperty which depends on the particulartribological system. In our case, the elements of thesmallest wear width occurred at input speedn 1 = 5000 min -1 . The reason for this is that the bestexperimental conditions, with regard to lubricationand wear, are at this input speed.6.2. WearA large pressure on surface does not lead to asudden failure of drive, but over the time, small324 13 th International Conference on Tribology – Serbiatrib’13