With respect to the application in unlubricated friction systems like dry clutches a commercially available, slightly porous monolithic alumina was modified using laser irradiation by embedding TiN particles. The materials development was carried out by experimental studies and numerical simulation. Temperature and velocity profiles of the molten alumina and the dispersed TiN particles during laser processing were calculated using a finite volume program (PHOENICS). Tribological properties of the modified ceramics were characterized in unlubricated sliding contact with the grey cast iron GJL-250 and the steel 100Cr6 using a pin-on-disc tribometer. Frictional and wear behaviour were analysed at varied sliding speeds. Commercial alumina and silicon carbide ceramics were used as reference materials.The friction and wear behaviour were determined by mechanical interactions, mainly abrasive processes, material transfer and formation of surface layers from densified wear particles, combined with tribochemical reactions. Sliding pairs with the lasermodified multiphase ceramics showed a greater wear resistance and a greater constancy of the friction coefficient with increasing sliding speed compared to the commercial Al 2 O 3 ceramic.Keywords
Analyzing wear mechanisms and developments of surface layers in WC/Co-cemented carbide cutting inserts is of great importance for metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the choice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously influences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc.), so the choice of optimised process parameters is of great relevance. Vapour-deposited coatings on WC/Co-cemented carbide cutting inserts are known to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood. The interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE 1045 steel workpiece was investigated during a dry plain turning operation with constant material removal under varied machining parameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM), and EDX analysis. The state of surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological processes in the cutting zone were examined by SEM and EDX analyses.
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