Marta Paczkowska

Laser boronizing and its potential application

This paper contains examples of machine components, the parts of which are exposed to intensive exploitation conditions. Thus, local surface layer modification of those parts is required to achieve appropriate properties. Laser treatments, including laser boronizing possibilities, are presented. The influence of laser boronizing on the surface layer structure of nodular iron components has been determined on the basis of the presented investigations. It has been proved that laser treatment makes possible implementation of boron in the surface layers of the treated material, and that such a method allows obtaining of a fine-crystalline, homogenous structure with iron borides. The microhardness of the surface layer of the samples studied after such treatment is increased by approximately five times.

EVALUATION OF THE HOMOGENEITY OF THE WORKINGSURFACE OF CAST IRON BRAKE DISCS

This article deals with the one of the most important elements of modern braking systems, which is a brake disc. A brake disc is the one of more stressed parts of the braking system, and its quality and design largely determine the braking performance of the vehicle. The article describes the technology of manufacturing disc brake pads that is important from the point of view of the wear processes occurring between two friction surfaces: the brake disc and the brake pad lining. The research of the cast iron ventilated brake disc surface measured the values of the selected roughness parameters at this site. In the context of measurements, it was also determined to be able to maintain a certain value of selected geometric parameters at a given location for the group of brake discs tested of a specific type and manufactured by a particular manufacturer. The work was carried out in the aspect of the research to create a surface layer to protect the brake discs from the effects of corrosive wear. Słowa kluczowe: chropowatość, żeliwo, tarcze hamulcowe. Streszczenie Artykuł dotyczy jednego z ważniejszych elementów współczesnych układów hamulcowych, którym jest tarcza hamulcowa. Tarcze hamulcowe są jednym z bardziej obciążonych elementów układu hamulcowego, a ich jakość i konstrukcja decydują w dużym stopniu o skuteczności hamulców w pojeździe. W części artykułu opisano technologię wytwarzania powierzchni roboczych tarcz hamulcowych ważną z punktu widzenia procesów zużyciowych zachodzących na styku powierzchni ciernej tarczy hamulcowej z powierzchnią cierną okładziny klocka hamulcowego. Wykonane pomiary powierzchni roboczej żeliwnych wentylowanych tarcz hamulcowych pozwoliły ustalić wartości wybranych parametrów chropowatości w tym miejscu. W kontekście pomiarów ustalono także zdolność do utrzymania określonej wartości wybranych parametrów struktury geometrycznej w danym miejscu dla grupy badanych tarcz hamulcowych określonego rodzaju i wyprodukowanych przez określonego producenta. Prace prowadzono w kontekście badań zmierzających do wytworzenia warstwy powierzchniowej zabezpieczającej tarcze hamulcowe przed skutkami zużywania korozyjnego.

Influence of operation on tram wheels and rails surface layer condition

Trams have become a constant in the landscape of many European metropolises in recent decades. The aim of presented research was to evaluate material changes in the surface layer of Siemens Combino, Konstal 105Na, Moderus Beta and Duewag GT tram wheels and rails as a consequence of wheel and rail exploitation in Poznan agglomeration. Microscopic study and hardness measurement were performed. The surface layer of tram wheel was highly deformed, particularly on the top of the wheel flange and under the rolling surface. In the tram wheel so-called overhangs on the top of the wheel flange and on the outer part of the rolling surface were found. Plastic deformation caused an increase of hardness in comparison to the core material. Hardness increase in case of the top of the wheel flange (even 60%) was bigger than in case of the rolling surface (up to 30%). It was also found that the longer approximate total mileage of the wheel was, the higher hardness increase of the surface layer was. ‘White layer’ as a result of presence of higher temperature during exploitation caused by friction was observed. Hard (even 2.5-times harder than the core material) and brittle layer can cause cracks. In case of Moderus Beta and Konstal 105Na wheels in the part from their frontal side decarbonization was noticed. It was stated that decarbonization is also present in the new wheel. It means that it is a defect of PST type wheel production. An area with so low hardness (below 100 HV0.1) could cause faster deformation and wear of whole wheel. A deformation in the surface layer were also revealed in rails. It was observed even in the coating area generated by welding — slip lines in austenite and martensite phase presence. Some recommendations for better wheel exploitation for Poznan Public Transport Company were also determined.