Developments in Sintered Piston and Sealing Rings

Sintered metal alloys have been used to supply the major proportion of the European requirement for shock absorber sealing rings in recent years, and the inherent self lubricating properties conferred by oil retaining surface porosity has proved to be most beneficial. Sintered sealing ring usage extends into other fields including automatic transmission systems and hydraulics.

Production of sintered rings has been developed at Brico to enable such features as chamfers and steps to be incorporated without secondary machining operations.

In the field of piston rings, a large number of small non-automotive engines such as lawn mowers, chain saws and outboard marine engines have used sintered alloys for many years, and the powder metallurgy process has proved to be very competitive. Where scuff resistance is a major factor, sintered rings perform well due to their oil retaining surface. This has naturally extended to automotive applications where sintered materials have worked well in many volume production motor cars.

This paper discusses recent advances in sintered piston and sealing rings aimed at producing alloys which perform at least as well if not better than the accepted wrought materials used at present in such applications as: - Compression rings in automotive internal combustion engines to replace hard chromium plated or molybdenum sprayed peripheral layers; Sealing rings in high duty shock absorbers where both high piston speeds and high side loading can cause scuffing and frictional problems with conventional materials; Sealing rings for both hot and cold ends of Turbocharger turbine shafts, where the powder metallurgy route can offer the benefit of effective lubrication by the addition of a solid lubricant to the matrix of the alloy during manufacture. This is of major importance In the case of the hot end ring which can run under very dry conditions due to high service temperatures.