Mikrostruktura a vlastnosti cementační vrstvy ozubených kol

Abstract

This thesis deals with an analysis of gear wheels, used in truck gearboxes. The gear wheels have been manufactured by forging and carburized. There have not been supplied any drawings or any other documentation for evaluated gear wheels. The theoretical part of this thesis deals with chemical and thermal processing in general, and then describes basic procedures of carburizing, including a description and evaluation of the carburizing layers. The experimental part of this thesis deals with an identification of unknown gear wheels, separation and collection of samples. The evaluation of gear wheels quality has been carried out in accordance with the standard ČSN ISO 6336-5. There has been used GDS emission spectroscopy for evaluation of chemical composition. Further, a metallographic evaluation of gear wheels melting purity has been performed, as well as microstructural analysis of the carburizing layer and teeth core, a metallographic evaluation of gear wheels surface state, an evaluation of original austenite grains size and a metallographic determination of the retained austenite. For each wheel has been measured hardness and effective depth of the carburizing layer and hardness of the teeth core. The results indicate that two gear wheels meet the highest quality of material and heat treatment, which ensures high operational reliability even under a high traffic load. Another two wheel gears showed serious deficiencies in both chemical composition and chemical-thermal processing.