Investigação sobr o uso da texturização a laser na preparação da superficie a ser recoberta em ferramentas de metal duro para fresamento / Research on the use of laser texturing for the surface preparation of to be coated carbide milling tools

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Machining is one of the fundamental manufacturing processes of contemporary industry and coated cemented carbide is the most used cutting tool material. Manufacturing of this kind of tools includes the substrate surface processing previously to coating deposition in order to achieve high adhesion resistance in the substrate-coating interface. The most spread out method with this intention is the substrate blasting with alumina micro-particles, which, although so widely used and effective, generates pollution, operator health risks, consumes considerable time and labor resources and presents roughness control difficulty. In the other hand, laser texturing is a surface engineering technology based on a pulsed laser which modifies the material surface through melting, evaporation, sublimation and subsequent solidification. This thesis aims to explore the laser texturing effectiveness as an alternative method for substrate surface pre-coating preparation. This process does not generate pollution, allows selective tool areas for processing and, being automated, it potentially requires less time and labor resources. The tools selected for the experiments were two kinds of coated cemented carbide with a composed TiCN+Al2O3+TiN MT-CVD coating and for the experimental substrate surface pre-coating preparation, a pulsed CuHBr laser was used. With the laser process dynamics used, it is possible to control the substrate roughness and to produce a great diversity of surface topographies and structures by adjusting the intensity and/or the amount of laser pulses. Also, it was verified that the laser processing always produces WC (present in the substrate) transformations in new non- stoichiometric phases with less C content. By trial and error method, two laser parameters sets were determined which produced the best adhesion resistance as evaluated through indentation tests: 02 pulses, 410 MW·cm-2 and 64 pulses, 239 MW·cm-2. In dry face milling cutting tests of mould P20 steel with toroidal tools, it was compared the performance of micro-blasted tools (commercial) against laser textured (experimental) ones finding an equal average life for both tool types. Detailed wear mechanisms analysis showed evidences in all the cutting edges of diffusion, attrition, abrasion, deformation, delamination, cracks and a secondary mechanism, called micro-melting wear of the material of the edge. There were no remarkable wear differences between the commercial edges and the experimental ones which could be attributable to the substrate surface pre-coating preparation process.

ASSUNTO(S)

aderencias surfaces (technology) machining metal cutting tools ferramentas para cortar metais superficies (tecnologia) usinagem adhesions

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