Project scope:

i) to establish a fundamental understanding of the role of the chemical composition and the manufacturing process on the material behaviour necessary to fulfil the demanding requirements of modern diesel engine valves, and

ii) to establish a toolbox including application of material characterisation techniques and methodology for addressing such kind of issues in general. In particular the corrosion properties will be addressed, whereby the environmental engineering with respect to internal combustion environment and life time of critical parts comprises the framework. Also, other properties of importance for the life time and performance of valves such as high temperature strength and fatigue will be considered.

The work is mainly of experimental nature using modern tools for material design. Diesel engines are under constant developments to meet the increasing environmental demands of reduced amount of NOx-gases and fewer particles in the exhaust gas. There are many actions taken to fulfil these demands and virtually all parts of the engines are affected.

One of the most challenging and complicated part of the engines is the valve, which regulates the intake of air and fuel mixtures and outlet of exhaust gases. This component experiences high loads from the gas pressure, high temperatures, high temperature fatigue (both thermal fatigue and mechanical fatigue loading) as well as wear from the contact between the valve seat and the seat insert material. It is also possible that corrosive species like sulphur and chlorine compounds may be present in the system with a subsequent risk of intergranular corrosion or stress corrosion cracking.

Improvements of the microstructure and properties of austenitic stainless steel valves require a detailed knowledge of the interplay between chemical composition of the alloy and the different stages the material experiences during the manufacturing. To obtain such knowledge, modern material design techniques like thermodynamic modelling and different kinds of microscopy and microanalytical methods must be employed (first objective).

However, it is also as important to be able to define the optimum combination of properties at the end of the production, which will give a maximised service life. By defining this, the goal for the alloy selection and production process can be set, whereby also a comprehensive toolbox is established for addressing this issue or other high-temperature service-related aspects in future (second objective).