Search Results

Powder metallurgy main bearing caps (MBC) are being used in General Motors 3100 and 3800 engines with over 1,500,000 bearing caps assembled to date. Powder metal was chosen to replace nodular iron because of its functional advantages and because its net shape capability eliminated major investments in bearing cap machining lines at General Motors. This paper explains the functional advantages of powder metal bearing caps. Grey cast iron, nodular cast iron and powder metal bearing caps are compared. Main bearing cap requirements of strength, fatigue life and consistency are discussed. The various experiments and durability tests used to develop powder metal caps are described.

Virtually all automotive systems are subject to intense commercial, market and legislative pressures to evolve in new directions. The exhaust system is no exception. The relentless drive to: reduce costs, to extend warranty and service life, to respond to customer cosmetic preference for bright metal under hood combined with emission legislation demanding zero leakage stretch the imagination and resourcefulness of the industry. Powder metallurgy (P/M) has a role to play in this regard. The complex and accurate net shape capability and material versatility of P/M provides an attractive combination for several components especially flanges. A hindrance, however, is lack of a materials property database relating to the special properties required for service. High burnt gas temperatures in exhaust systems produce internal corrosion oxidation attack, and stress relaxation of joints while road salt attacks the external surfaces.