| The investigation of this study is concerned with three main topics. One is the improvement of the nozzle lifetime for abrasive water jet (AWJ) machining. The second one is the thermal shock effect on nozzle wear. The last one is the characterization of WC-Ni wear resistant coatings deposited onto steel substrates by plasma transferred arc (PTA) hardfacing.; In the first part of the study, the mechanisms of nozzle wear were investigated and a series of AWJ tests were performed on several hot pressed hard materials. The volume losses of different materials were compared and the effects of the materials properties on the lifetime of the focusing tube were analyzed. As an alternative approach to improve nozzle lifetime, a ROCTEC100 nozzle was coated with a thin film of diamond by chemical vapor deposition (CVD) for better wear resistance. The diamond film proved to be effective in improving the nozzle performance for a short duration test.; To determine the thermal shock effect on the wear loss of the hard materials, the maximum temperature of the cutting interface was measured by an optical pyrometer and a thermocouple, respectively, during the 10 degree abrasive waterjet tests. Theoretical heat transfer computation under steady state conditions was also conducted using numerical methods.; Finally, several WC-Ni coatings deposited by PTA were characterized and the wear mechanisms determined. The carbide size, mean free distance between carbides, coating porosity, iron dilution content and hardness were measured and a variety of analyses were carried out to try to find a correlation with the wear test results. Finally, the effects of PTA process parameters on the coating wear performance were investigated. |
