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In this investigation, worn valve seats and inserts have been examined to obtain a fundamental understanding of the primary wear mechanisms. Seats and inserts from a wide variety of engines were studied using optical and electron microscopy. The recessed region on seats and inserts displayed a common feature which can be described as a series of ridges and valleys formed circumferentially around the seat axis. These ridges and valleys were found to be due to either a relatively severe gouging process or to a milder deformation and wearing process. These processes were related to assembly and product geometry factors which caused misalignment between the seats and inserts.

In this investigation, more than one hundred valves from forty seven fired engines have been examined. The worn surfaces of valve and insert seats from a wide variety of engines were studied using optical microscopy, SEM and EDX. The purpose of this investigation is to obtain a fundamental understanding of the primary wear mechanisms on the valve/insert seat of the engines. The wear mechanism which dominates the valve/insert seat wear depends on the engine operating conditions, seat contact configurations, valve/insert seat materials, and dynamics etc. Besides adhesion, corrosion and abrasion wear mechanisms, this study also found that shear strain is a major factor contributing to engine valve/insert seat wear. When shear strain at the seat surface exceeds the limit of the material, delamination wear is produced.