Standing contact fatigue analysis of steels with different

University essay from Luleå/Applied Physics and Mechanical Engineering

Abstract: High performance steels has been studied in this master thesis. The
main objective was to understand the contact fatigue resistance of one
silicon containing steel which can be treated in order to give it a carbide
free bainitic microstructure.

Different microstructures of the steels were produced by
austenitizing followed by different cooling cycles as austempering processes
with which microstructures with high strength, good ductility, high
toughness and excellent wear resistance can be achieved.

The work is divided into three-main parts. The first part treats the
production of different micro structure as austenitic-ferritic structure,
fully pearlitic, fully martensitic, quenched & tempered and lower bainitic
structure respectively, including metallographic observations.
The second part treats the special Standing Contact Fatigue (SCF) analysis
used in the work, which consists of cyclic loading of a hard ball in contact
with the flat surface of the specimen, which is meant to simulate asperity
contact in surface contact fatigue analysis.

The third part deals with the characterization and analysis of the results
obtained for the ausferritic and the other microstructure in the work.
The experimental results have shown that the ausferritic structure has a
very good combination of material properties like good contact fatigue
resistance, high strength, ductility and toughness properties.
The microstructure before and after the tests were analyzed with the help of
Optical microscopy, SEM microscopy, XRD analysis and additional analysis was
performed by micro hardness measurements.