AbstractThis paper shows successful hindering of the negative effects of the cobalt binder in the process of coating WC-Co cutting tools with CVD diamond films. The strategy was creating a boron-rich layer on the surface of the WC-Co substrates as an interlayer to block Co migration. The traditional boriding technique was improved by preheating the salt powders and controlling the brittle region thickness in the substrate surface. These procedures produce a tougher surface for diamond growth. Adding CF4 to the gas mixture also enhanced diamond adhesion to the surface. The adhesion of diamond films to WC-Co substrates was evaluated by indentation tests. Samples were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), X-ray Diffraction (XRD) and Raman Scattering Spectroscopy (RSS).

Realizaram-se crescimentos de filmes de diamante por deposição química de vapor (CVD, do inglês Chemical Vapor Deposition) em substratos de silício (100), de grande área (80 cm²), em um reator de filamento quente (HFCVD), com taxas de crescimento superiores a 1,5 µm/h. Foi realizado o crescimento das amostras com diferentes fluxos gasosos e diferentes porcentagens de metano (CH4) em hidrogênio (H2). As amostras foram caracterizadas por microscopia óptica, eletrônica de varredura e por espectroscopia de espalhamento Raman. Tais análises acusaram a presença de diamante de alta pureza em todas as amostras.

Diamond films were grown through Chemical Vapor Deposition (CVD) in silicon substrates (100) of large area (80 cm²), in a hot filament chemical vapor deposition (HFCVD), with growth rates over 1,5 µm/h. The growth of samples was made with different gaseous fluxes and different methane percentages (CH4) in hydrogen (H2). The samples were analyzed through optical microscopy, Scanning Electron Microscopy and Raman spectroscopy scattering. Such analyzes showed the presence of a high purity diamond in all samples.

O preparo dos substratos, para o crescimento de filmes de diamante CVD, é de fundamental importância por diversos fatores. Um novo método de preparação dos substratos de molibdênio, o jateamento por óxido de alumínio, é apresentado e comparado com os métodos tradicionais de preparo. As amostras de diamante CVD obtidas foram analisadas por espectroscopia de espalhamento RAMAN e por microscopia eletrônica de varredura (MEV). Obtiveram-se filmes de diamante CVD de boa qualidade e uniformidade e o novo processo proposto de tratamento do substrato de molibdênio permitiu maior taxa de crescimento que os métodos tradicionais.

The substrate preparation for CVD diamond growth is of basic importance due to several reasons. A new molybdenum substrate preparation method, the aluminum oxide abrasion jetting, is introduced and compared with the traditional ones. Raman Scattering Spectroscopy (RSS) and Scanning Electron Microscopy (SEM) characterize CVD diamond films. CVD diamond films of good quality and uniformity were obtained. The substrate preparation by aluminum oxide blasting allowed for a higher nucleation rate.

Surfaces with very poor mechanical and frictional properties can be improved, or even, acquire new properties similar to diamond if good adherent CVD diamond film is obtained on it. In this work, nitrogen ions were sub-implanted on pure molybdenum as a means to enhance CVD diamond film adherence. Deposition time from 2 up to 60 h were used for deposition of 10 to 400 µm thick CVD diamond films with very good adherence on sub-implanted molybdenum substrate. Characterizations were carried out by XPS, X-ray diffraction and nano indentation on prepared surfaces prior to diamond growth and after the onset nucleation. The ionic sub-implantation with nitrogen possibly assists in adhesion, with the creation of a thin layer of nitrates and complexes.