TY - THES

T1 - Thermochemical Surface Treatment for Wear and Corrosion Resistance

AU - Hollerweger, Robert

N1 - embargoed until 26-05-2015

PY - 2010

Y1 - 2010

N2 - Thermochemical surface treatment is a common method to enhance wear and corrosion resistance. Coatings prepared with such a process on different substrate materials as well as influences and risks of the process itself were studied in this thesis to explore the limits for application possibilities and enable implementation in improved machinery. The coatings were obtained by pack cementation using a powder of metal, filler and ammonium halide and process temperatures around 1000°C. Soft-chromising of low carbon steels resulted in improved corrosion resistance. The effect of substrate chemistry on the formation of chromium carbide layers employing hard-chromising was investigated by using a carbon steel, tool steel, stainless steel and different case hardening steels. The low carbon containing materials were pre-carburised and all samples were argon gas hardened after the chromising treatment. Additional studies on the influence of pre-carburising, chromising time and hardening parameters on the layer formation and performance were conducted on a case hardening steel using no pre-carburisation, 125% process time and oil hardening. These samples were investigated with a focus on corrosion behaviour, the structure (e.g. by Electron Back Scatter Diffraction (EBSD)), mechanical properties (mainly by indentation experiments) and wear resistance. This comprehensive study on the influence of substrate materials, pack cementation process, pre-carburisation and after-treatment hardening provides basic knowledge to be used for application driven materials design.

AB - Thermochemical surface treatment is a common method to enhance wear and corrosion resistance. Coatings prepared with such a process on different substrate materials as well as influences and risks of the process itself were studied in this thesis to explore the limits for application possibilities and enable implementation in improved machinery. The coatings were obtained by pack cementation using a powder of metal, filler and ammonium halide and process temperatures around 1000°C. Soft-chromising of low carbon steels resulted in improved corrosion resistance. The effect of substrate chemistry on the formation of chromium carbide layers employing hard-chromising was investigated by using a carbon steel, tool steel, stainless steel and different case hardening steels. The low carbon containing materials were pre-carburised and all samples were argon gas hardened after the chromising treatment. Additional studies on the influence of pre-carburising, chromising time and hardening parameters on the layer formation and performance were conducted on a case hardening steel using no pre-carburisation, 125% process time and oil hardening. These samples were investigated with a focus on corrosion behaviour, the structure (e.g. by Electron Back Scatter Diffraction (EBSD)), mechanical properties (mainly by indentation experiments) and wear resistance. This comprehensive study on the influence of substrate materials, pack cementation process, pre-carburisation and after-treatment hardening provides basic knowledge to be used for application driven materials design.

KW - wear corrosion chromising boriding EBSD nanoindentation

KW - Verschleiß Korrosionsschutz inchromieren borieren EBSD nanoindentation

M3 - Diploma Thesis

ER -