Investigation of Exhaust Valve Failure in Heavy - duty Diesel Engine

The exhaust valves of a diesel engine are exposed to thermal and mechanical overstress which may be sources of valve failures. The exhaust valves usually fail as a result of different failure modes such as wearing, fatigue and corrosion. In order to describe these modes a failed exhaust valve which was belonged to a heavy-duty diesel engine is investigated. The investigation of the failure was carried out by using several experimental tests including optical emission spectroscopy, optical microscopy, scanning electron microscopy SEM and EDX. It was found that the carbon content of the material of the failed valve decreased. Angular titanium phases were found in microstructure of the material of the failed valve. Fuel-born vanadium and chromium carbide were detected on the surface of the valve. It was concluded that the valve was broken down before its expected service life.