30 Credits - Influence of matrix and alloying on the high cycle fatigue properties of compacted graphite iron for cylinder heads i Sodertalje

Scania genomgår nu en transformation från att vara en leverantör av lastbilar, bussar och motorer till en leverantör av kompletta och hållbara transportlösningar.

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Background:
The continued improvements on the combustion processes and introduction of biofuels as well as requirements of decreasing fuel consumption and increasing specific power will inevitably lead to an increase of the combustion pressure, which ususally also is accompanied with a temperature increase. This will in turn increase the loading on many components and drives the development of materials more resistant to the harsh conditions close to the engine. The cylinder head is one of the components that will be affected by the increased loads. In this respect both thermomechancial loads originating from the cyclic temperature variations from the heating up and cooling down cycles of the engine and the high cycle fatigue load emanating from the repeated combustion pressure pulses are relevant and may cause failure of the component. Today, most cylinder heads for heavy trucks are cast in either lamellar graphite iron (LGI) or compacted graphite iron (CGI). In both cases the graphite particles are embedded in a pearlitic matrix. However, a possible improvement of the endurance life of the component is to introduce a more ferritic matix. The hypotheis is that the more ductile ferritic matrix enclosing the graphite particles will improve the resistance to macro crack initiation and propagation and thus the life of the component. The purpose of this master thesis is to investigate the effect of a ferritic matrix as well as added alloying elements such as molybdenum and nickel on the high cycle fatigue properties of CGI.  

Target:
The purpose of this thesis proposal is to investigate the effect of a fully or partially ferritic matrix possibly also alloyed with molybdenum or nickel on the high cycle fatigue properties of CGI. The fatigue life will be determined including also the sensitivity to mean stress as well as notches and defects. The results will be compared with findings on a conventional CGI alloy with a pearlitic matrix. An important part of the work will be to investigate and characterize the different microstructural constituents of the alloys and relate them to the fatigue performance.  

Assignment:
The work will be initiated with a literature study concerning the influence of  matrix and alloying on both the fatigue life and the static properties. Thereafter, specimens will be selected from the comprehensive casting series conducted at the Scania foundry during the fall of 2019. The selected specimens will be characterized with respect to composition, static properties, hardness, microstructure and fatigue performance. The project results will be presented both in writing and orally.

Education:
Master of Science or equivalent: Mechanical Engineering/Materials Engineering/Engineering Physics
Number of students: 1
Start date: As agreed
Estimated time needed: 20 weeks

Contact person and supervisors:
The work is performed at Materials Technology in Södertälje, Sweden. Contact persons/supervisors
Peter Skoglund, tel: +46 (0)8 553 86 285,

• Title: 30 Credits - Influence of matrix and alloying on the high cycle fatigue properties of compacted graphite iron for cylinder heads
• Business area: Research and Development
• Country: Sweden
• City: Sodertalje
• Last application date: 2020-01-10
• Job Id: 20194779