High temperature wear behaviour austenitic and martensitic stainless stell

ABSTRACTM.Sc.ThesisHIGH TEMPERATURE WEAR BEHAVIOUR AUSTENITICAND MARTENSITIC STAINLESS STELLMurat GÜRKANAfyonkarahisar Kocatepe UniversityGraduate School of Natural and Applied SciencesDepartment of Metal EducationSupervisor: Asst. Prof. Şükrü TAKTAKStainless steels are mainly used for corrosion resistance applications. It is, however,rarely used for tribological applications such as wear because of poor surface hardnessand low load bearing capacity. Great efforts have been made improve its surfaceproperties. In this study, high temperature wear properties of borided AISI 420 and 304stainless steels were investigated. Boriding heat treatment was carried out using a packboriding method in an electrical resistant furnace at 900ºC for 5 h. The morphology ofboride layers formed on stainless steel was observed by use of an optical microscopy.The presence of borides formed in coating layer was confirmed by means of X-raydiffraction. Hardness of the boride layers were assessed by micro-Vickers indentationsusing a Vickers micro-hardness tester. High temperature wear tests were carried out intoa furnace, which was placed on wear test setup, at room temperature, 300ºC and 600ºC.Wear tracks of the worn samples were examined.iiiX-ray diffraction results showed FeB, Fe2B, CrB, Cr2B and Ni3B phases on 420 steeland FeB, Fe2B, CrB and Cr2B phases on 304 steel. Oxide forming was observed onborided and unborided steel with the increase in temperature. It is observed that wearrate of unborided steels increased 7 to 8 times at high temperature compared with roomtemperature, while this increase was 2 to 3 times for borided steels.2007, 67 pagesKeywords: Stainless steel, boriding, High temperature weariv