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Against the background of environmental problems, the market for variable nozzle turbochargers, which enable countermeasures for improved fuel economy and exhaust gas regulations, has grown rapidly in recent years. Because the nozzle ring is a main part which is used under a particularly severe temperature environment, even among turbocharger parts, high Cr cast steel is generally used. In response to market needs for further improvement in heat resistance and cost reduction, EW-50 which has heat resistance and wear resistance was developed, as this material is suitable for parts such as nozzle rings. EW-50 has higher wear resistance and oxidation resistance than the conventional high Cr cast steel over the entire temperature range up to 1323K. As EW-50 also makes it possible to reduce costs by near net shape production, its large potential for application to variable nozzle-type turbocharger parts was confirmed.

Sintered materials have been applied widely for Valve Seat Inserts (VSI) due to their high flexibility of material design. Hard particle dispersion type materials, which have specific microstructures in sintered material, are popular for VSIs. The load - temperature, combustion pressure, etc. - on the VSI has become severer along with increasing demands for better engine performance. (1) Especially, there is increasing tendency of the amount of wear on VSIs when used in heavy-duty engines such as diesel/gas (LPG, CNG) engines because of their dry environments.(2) In this paper, two new developed high performance VSI materials for heavy-duty engines are introduced. These materials adopt new hard particles and a new method of distribution of the solid lubricant to increase wear resistance. Hard Particles: The new developed hard particle has superior wear resistance due to increasing the amount of intermetallic compounds.

Generally, cobalt-contained sintered materials have mainly been applied for exhaust valve seat inserts (VSI). However, there is a trend to restrict the use of cobalt as well as lead environmental law, and cobalt is expensive. To solve these problems, a new exhaust VSI on the assumption of being cobalt and lead free, applicable for conventional engines, having good machinability, and with a reduced cost was developed. The new exhaust VSI is a material dispersed with two types of hard particles, Fe-Cr-C and Fe-Mo-Si, in the matrix of an Fe-3.5mass%Mo at the ratio of 15 mass % and 10 mass % respectively.

The demands on valve seat insert materials, in terms of providing greater wear-resistance at higher temperatures, enhanced machinability and using non-environmentally hazardous materials at a reasonably low cost have intensified in recent years. Due therefore to these strong demands in the market, research was made into the possibility of producing a new valve seat insert material. As a result a high speed steel based new improved material was developed, which satisfies the necessary required demands and the evaluation trials, using actual gasoline engine endurance tests, were found to be very successful.