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Aluminium-rich Ti(1-x)Al(x)N coatings by CVD
The performance of cutting tools can be increased by wear resistance coatings with improved properties. Up to now hard Ti(1-x)Al(x)N coatings with the NaCl structure have been prepared industrially by PVD (physical vapour deposition) processes with a maximum x=0.65. Higher x lead to the co-deposition of the softer hexagonal wurtzite phase. In this work the preparation of fcc-TiAlN (face centered cubic) coatings with x up to 0.9 by thermal CVD (chemical vapor deposition) is described for the first time. A LPCVD (low pressure chemical vapor deposition) process using TiCl4, AlCl3, NH3, H2, N2 and Ar is applied. At deposition temperatures between 700 deg C and 900 deg C very hard Ti(1-x)Al(x)N layers with 0.8 < x < 0.9 were prepared. The layers possess a high hardness between 3000 HV and 3300 HV and a Young's modulus up to 540 GPa. In first wear tests a high performance of the CVD-Ti(1-x)Al(x)N is observed. Coated inserts show a reduced wear by 30 % in comparison with astate-of-the-art PVD coating in reaming of steel and cast iron.