TiAlN

Other coatings, such as TiAlN (96), TiCN, Zr02, and ZrN (97), and CrN (98) were developed for special appHcations. The last was developed for higher speed machining of titanium alloys. Sometimes a coating is developed not for its wear-resistance but for its heat insulation. The case in point is alumina coating of cBN to reduce the heat conductivity at the surface so that the cBN performance can be enhanced (99). 

Different TiN-, TiC-, and TiAlN-based single layer coatings on steel alloyed with Cr, Ni, Mn, and WC were prepared by use of the cold vapor deposition technique. The thickness of the coatings varied from 2.7 to 6.4 pm. 

Two detection techniques were tested, LIBS for the Cu-Ag-Si samples and LA-TOF-MS for the TiN-TiAlN samples. 

The "soft" ablation of the TiN-TiAlN samples by the low fluence laser beam was performed by use of LA-TOF-MS. Because of the greater sensitivity of this technique compared with direct LIBS the lower laser fluence of approximately 0.3-0.4 J cm was used. One of the depth profiles, obtained by use of femtosecond LA-TOF-MS, is shown in Fig. 4.44. Each 280-nm-thick layer was ablated by approximately 20-25 pulses, which result in an average ablation rate of 11-14 nm pulse . The ablation rate was low enough for resolution of all layers. 

The crater surfaces obtained in the LA-TOF-MS experiment on the TiN-TiAlN-Fe sample were remarkably smooth and clearly demonstrated the Gaussian intensity distribution of the laser beam. Fig. 4.45 shows an SEM image of the crater after 100 laser pulses (fluence 0.35 J cm ). The crater is symmetrical and bell-shaped. There is no significant distortion of the single layers. Fig. 4.45 is an excellent demonstration of the potential of femtosecond laser ablation, if the laser beam had a flat-top, rather than Gaussian, intensity profile. 

Lewis, D.B., Wadsworth, I., Mtinz, W.-D., Kuzel, R. and Valvoda, V. (1999), Structure and stress of TiAlN/CrN superlattice coatings as a function of CrN layer thickness , Surface and Coatings Technology, 116-119, 284-291. 

TAP triallyl phosphate TiALN titanium aluminum nitride... 

Fig. 18. Deconvoluted XPS O (Is) and spectra of ambient (Ti,Al)N thin films, (a) TiAlN film short-term oxidized at 850 °C and (b) TiAlN film long-term oxidized at 850 °C. Possible peak identification 1) Ti02 2) AI2O3 3) mixed oxynitrides 4) absorbed OH 5) mixed oxides. Reprinted with permission from S. Seal et al., J Vac. Sci. Technol. A18(4), 1571, 2000, in press. Copyright (2000), American Vacuum Society.

Figure 8. Friction coefficients against normal load for MeC H, TiN, TiAlN and steel measured against ball bearing steel under ambient conditions (up to about 50% relative humidity).

TiAlN, or similar coatings. In addition to being more wear resistant, such coatings minimize the friction between tool and hole surface as well as between tool and chips. Under finishing conditions with solid tungsten carbide drills, it is possible to achieve diameter qualities in the range of IT 7-IT 9 and a surface roughness of Rz = 2-4 pm in special cases, = 1 pm. 

Physical Vapor Deposition (PVD), Fig. 5 SEM cross section micrographs of (a) a Ti35A165N fine-grained coating, (b) a Y-AI2O3 coating on a TiAlN film, and... 

Solid carbide drills, taps and end milling cutters are available for cutting a wide variety of materials. Some have a surface coating such as titanium aluminium nitride (TiAlN) which fiirther enhances cutting performance, offering different levels of surface hardness, thermal and frictional properties. 

To enhance their cutting performance, some taps have surface coatings of titanium aluminium nitride (TiAlN) and titanium carbon nitride... 

Allhough the majority of end-milling cutters are manufactmed from HSS and HSCo, some with hard surface coatings, soUd carbide cutters are available, also with surface coatings which include titaniiun aliimin-ium nitride (TiAlN) to further enhance their cutting performance. 

Katahira, K., Watanabe, Y., Ohmori, H., and Kato, T., ELID grinding and tribological characteristics of TiAlN film. International Journal of Machine Tools and Manufacture, Vol. 42, 2002, pp. 1307-1313. 

To account for a coated tool, the tool was coated with a 4 im thick TiAlN coating all other computational parameters were identical. The results can be seen in Figure 13.7. 

Souto RM, Alanyali H (2000) Electrochemical characteristics of steel coated with TiN and TiAlN coatings. Corros Sci 42 2201-2211... 

Subramanian B, Muraleedharan CV, Ananthakumar R, Jayachandran M. A comparative study of titanium nitride (TiN), titanium oxy nitride (TiON) and titanium aluminum nitride (TiAlN), as surface coatings for bio implants. Surf CoatTechnol 2011 205(21-22) 5014-20. 

Coated carbide tools are known to perform better than uncoated carbide tools. Thus commercially available CVD coated carbide tools were used in this investigation. The tools used were flat end mill cutters produced by WIDIA (EM-TiAlN). The tools were coated with TiAlN coating. For each material a new cutter of same specification was used. The details of the end milling cutters are given below ... 

Fig. 7. SEM micrograph of deposited TiAlN coating with typical columnar structure and pyramidal tips (a) top view of coating and (b) coating edge. Copyright by Elsevier. Reproduced with permission.

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