Tham khảo tài liệu 'modeling and simulation for material selection and mechanical design part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Figure 26 Fourier transform from EELFS analysis of a wear crater TiCrN coating on nitrided T15 steel a cutting time 30 sec b cutting time 180 sec c cutting time 2100 sec. Copyright 2004 by Marcel Dekker Inc. All Rights Reserved. transform. The first peak is now located at a distance while the second peak is at a distance R2 Ả. These peaks correspond approximately to the length of C-Fe and Fe-Fe bonds RC RFe Ả RFe RFe Ả . The spectrum shown in Fig. 26c is typical of the BCC-lattice of T15 high-speed steel. B. Tribological Properties and the Metallurgical Design of Surface-Engineered Tools The study of the wear resistance of coated tools demonstrates that the protective role of the coating is most efficient when the effects of the work of cutting can be localized in the near-surface region of the coating 43 . Current coating technologies achieve this goal by modifying the energy distribution from the tool surface into the chip and by promoting the selforganization of the tool. This is done in two ways 1 by surface engineered and self-lubricated coatings for low and moderate speed machining and 2 by the use of hard or superhard coatings that can act as thermal barriers and form very stable tribo-ceramics at the surface during high-speed cutting. 1. Surface-Engineered or Duplex Coatings The principal application of these coatings 45 is for cutting at low speeds when HSS and DCPM tools are used. It is desirable to deposit the hard coating not directly onto the steel substrate but rather onto an engineered sublayer so that a gradual change in properties at the coating-substrate interface . a functionally graded material is realized. This sublayer can be obtained by different technologies . ion nitriding. Usually such coatings will then include both a nitrided sublayer and a hard PVD coating. The nitrided sublayer has two roles. It prevents intensive plastic deformation of the substrate HSS or DCPM and cracking of the PVD .
