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The analysis of the wear resistance of engine components must take into account the whole system. It is of no use to improve the properties of one of the components if it will cause higher wear on the other components of the tribological system. This paper presents a study to improve the wear resistance of piston ring coatings and liner materials at the same time that the compatibility between their wear rates is focused. The diesel engine tests were run with high sulfur fuel (about 0.9 wt%) and lubricant with low total base number (TBN) with the objective of increasing the corrosive conditions. The results show that the best compatibility between the wear rates of the top rings and liners is achieved when the rings are coated by plasma spraying with a molybdenum based material containing approximately 15% of moly carbide and when the liners are made of pearlitic gray cast iron with niobium, vanadium and titanium additions.

The components of the piston/ring/liner system must have their wear resistance increased to meet the new engine requirements. The engine operating conditions can be even worse if corrosive wear in the engine is expected to occur. This paper presents a study to improve the wear resistance of piston ring coatings and liner materials by the addition of chromium carbide and carbide forming alloying elements, respectively. The engine tests were run with high sulfur fuel (about 1.0 wt%) and lubricant with low total base number (TBN) with the objective of increasing the corrosive conditions. The results show the improvement of the ring coatings wear resistance with the increase of the chromium carbide content. The cylinder liner materials also presented lower wear rates when they had hard particles, mainly due to the addition of niobium, vanadium and titanium.

The evolution of internal combustion engines has led to friction reduction as well as to gaseous emissions reduction, demanding the use of narrower rings. Nodular cast iron is used satisfactorily for compression piston rings, with wear resistant coatings to improve their durability. However, for more severe applications and rings narrower than 1.2mm, even the nodular cast iron mechanical resistance is not enough. In this way, the use of steel is recommended, which may have its tribological properties improved by the nitriding thermochemical treatment. This paper presents the characteristics of the materials and of the nitriding process of compression and oil control rings as well as bench and dynamometric test results run during the development of these products.

The higher load in heavy duty Diesel engines and the use of piston ring coatings with higher wear resistance cause more severe working conditions to the cylinder liners. In some cases, high localized wear occurs at the top dead center (TDC) of the first groove ring, where the loads and lubrication conditions are critical. It was studied the effect of the addition of hard particles on cylinder liner materials. The presence of these particles was obtained through the use of small quantities of strong carbide forming alloying elements: Vanadium, Niobium and Titanium. Cylinder liners with hard particle addition were tested in comparison to regular liners. This test used high sulfur fuel (> 1.0 wt %) and low additivation lubricant oil, maintaining the same ring pack configuration for both liners. The results showed sensible liner wear reduction at the TDC of the first ring without compromising the ring pack performance.