Metallurgical Stability of Articulated Piston Under Severe Engine Operating Condition

This paper analyzes the surface metallurgical transformation (such as oxidation, sulfidation and decarburization) and/or bulk metallurgical transformation (such as overtempering of tempered martensite structure, spheroidization or graphitization of carbides) which may occur during articulated piston operation in high loaded diesel engines.

The evaluations performed on pistons that operated on high loaded engines (field and dyno) indicate that no bulk metallurgical transformation occurs on the SAE 4140 steel for temperatures up to 550 °C and that the only surface metallurgical transformation observed is the oxidation. This oxidation layer, at the levels observed on the analysed pistons, has no detrimental strucutural influence.