Wear and degradation of rock drill buttons with alternative binder phase in granite and sandstone

Abstract: In this thesis, drill bit buttons with cobalt, nickel and iron binders in different compositions have been tested against granite and sandstone and the wear and friction have been measured. Furthermore, the wear and degradation of the buttons have been categorized. Buttons with cobalt binder were tested against granite and sandstone and buttons with alternative binders (Ni, Fe, Co) were tested against granite. Cobalt buttons were used as a reference and the wear and friction of the alternative binders was compared to the reference. The amount of worn rock was also measured. Furthermore, post treated drill bit buttons with a composition of Fe-Ni-Co were compared to buttons with the same composition that had not been post treated The results show that buttons with an alternative composition of Fe-Co-Ni and Fe- Ni wears less than the cobalt reference. The post treatment process does not decrease the wear of the drill bit but lowers the deviation from the mean wear. The amount of worn rock does not differ between the samples except for between the post treated and not post treated buttons with a composition of Fe-Ni-Co. The post treated buttons produces more rock debris than the not post treated. No apparent difference could be seen on the surface of the tested buttons after the test. However, composition specific cracks could be found underneath the surface of the samples. EDS-analysis showed signals of oxygen inside of all of the investigated cracks. For some compositions at depths of 20 micrometers. The curves of friction shows similar appearance but the values of the coefficient of friction differs. No apparent correlation was found between the wear and friction of the samples. Furthermore, no apparent correlation was found between the hardness and the wear of the buttons.