High Performance Valve Seat Materials for CNG Powered Combustion Engines.

Andrzej Romański,Elżbieta Cygan-Bączek

doi:10.3390/ma14174860

Andrzej Romański, Elżbieta Cygan-Bączek

Open Access

https://doi.org/10.3390/ma14174860

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Abstract

The conventional copper infiltrated high speed steel (HSS) valve seats used in gasoline engines are not suitable for CNG combustion because the exhaust gas temperature is at least 80 °C higher, which drastically shortens the service life of the engine valves. Therefore, a proprietary high-alloy HSS-base material was designed to combat hot corrosion and mechanical wear of valve seat faces in CNG fuelled engines. A batch of −100 mesh water atomized HSS powder was commissioned. The powder was vacuum annealed in order to reduce oxygen content and increase its compressibility. To improve the final part machinability, 1.2% MnS was admixed to the HSS powder prior to compaction. The green compacts were sintered at 1135 °C in nitrogen to around 83% TD and subsequently infiltrated with a copper alloy. After installing the valve seat components on a cylinder head, the engine was tested for 100 h according to the automotive industry valve seat wear test procedures. Both the periodic 8-h checks as well as the final examination of the valve seats showed very slow wear, indicating their suitability for CNG powered engines.

Highlights

To meet high temperature resistance to wear of valve seat, a new high speed steel (HSS) powder was developed to ensure sufficient amount of carbides in the microstructure between 900 and 1200 ◦ C, mainly MC and M6 C type, which guarantee a high performance of the steel at elevated temperatures
In order to calculate the porosity of the investigated materials, the theoretical density was estimated on the basis of the rule of mixtures
The presented research programme is of high importance, especially when valve seats wear test results are considered

Summary

Introduction

Academic Editors: Filippo Berto, Andrey Belyakov and Tao-Hsing Chen. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. As a results of introducing the new WLTP homologation process and the need of reducing pollution and decarbonisation across the transport sector, a strong interest in using compressed natural gas (CNG) or liquefied natural gas (LNG) as a fuel for powering vehicles is observed, especially in public transport, trucks and passenger cars. According to the Vehicle Catalogue 2019, there are 68 gas vehicles currently available in Europe, from passenger cars and light commercial vehicles to heavy-duty trucks and buses. The number of registrations of new CNG powered cars recorded in the EU in 2019 approached 83,000.

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