Influence of Cryogenic Temperatures on Mechanical Properties of Valve Seats of Internal Combustion Engines

Abstract

Valve seats of internal combustion engines are used in cylinder heads, due to increase the strength and abrasion resistance of the intake and exhaust valve seats. Valve seats are made from alloy cast iron, high-alloy steels, wear-resistant alloys and seats made using powder metallurgy. The valve seats are pressed into the head. Some materials must be deep-frozen before pressing to reduce the pressing overlap. The overlap is large, in the order of tenths of a millimetre, due to the guaranteed seating of the seat in the cylinder head. The amount of overlap depends also on the material of the cylinder head. Liquid nitrogen (about -196 °C) is used for freezing. In our case, these are monometallic seats, made by technology of precision casting from cobalt alloys. A particular type of cobalt alloy uses the trade name STELLITE.