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The superior fuel economy of diesel engines compared to gasoline engines is favorable in reducing carbon dioxide (CO2) emissions. On the other hand, the reductions in nitrogen oxides (NOx) and particulate matter (PM) emissions are technically difficult, thus the improvement in the emission reduction technologies is important. Although the cooled exhaust gas recirculation (cooled-EGR) is the effective method to reduce NOx emissions, it is known to have durability and reliability problems, especially of the increased wear of piston rings and cylinder liners. Therefore, the degree of cooling and amount of EGR are both limited. To apply the cooled-EGR more effectively, the wear reduction technology for such components are indispensable. In this study, the negative effects of cooled-EGR on the wear are quantified by using a heavy-duty diesel engine, and its wear mechanism is identified.

Engines are assigned big subjects such as low emission and low fuel consumption as well as higher output (higher efficiency) in the latest trend of environmental protection. In order to meet these requirements, Air/Fuel ratio of recent high performance engines is being arranged leaner than that of conventional engines. As a result exhaust valve seat inserts used in these engines have problems of their wear resistance because of high exhaust gas temperature. By analyzing wear mechanism under the lean burn conditions, authors developed material for exhaust valve seat inserts which show superior wear resistance under high operating temperature. For the purpose to enhance heat resistance, authors added alloy steel powder for matrix powder and used hard particles which have good diffusion with matrix. The developed material does not include Ni and Co powders for cost saving and has superior machinability.