Environmentally Benign Micro Scale Cutting Tools for Nanotechnology Applications

摘要

Cation-substituted Ti_(1-x_y-z)Al_xCr_yY_2N alloys, with y = 0.03 and z =0.02, have been shown to offer enhanced high-temperature oxidation resistance compared to presently used TiN and Ti_(1-x)Al_xN films. Layers (3 mu m thickness) were deposited by unbalanced magnetron sputter deposition to small grain WC-Co unused cutting tools which had been ion etched in situ using a steered Cr-metal-ion cathodic arc discharge at an Ar pressure of 6 X 10~(-4) mbar (0.45 mTorr). The metal ion-etching promoted initial local epitaxy on individual substrate grains while the overall film texture evolved through competitive growth to (111) in Ti_(0.44)Al_(0.53)Cr_(0.03)N alloys and (200) in Ti_(0.43)Al_(0.52)Cr_(0.03)Y_(0.02)N. Although Ti_(0.04)Al_(0.53)Cr_(0.03)N layers exhibited a columnar microstructure similar to that previously observed in Ti_(1-x)Al_xN alloys, the addition of 2 mol percent YN resulted in significant grain refinement giving rise to an equiaxed structure. The Knoop microhardness of Ti_(0.43)Al_(0.52)Cr_(0.03)Y_(0.02)N alloys was HK_(0.025)=2700 kg mm~(-)2 compared to 2400 kg mm~(-2) for Ti_(0.04)Al_(0.53)Cr_(0.03)N. The onset of rapid oxidation, as determined from thermo-gravimetric measurements, ranged from 600 deg C for TiN; 870 deg C for Ti_(0.466)Al_(0.54)N; 920 deg C for Ti_(0.04)Al_(0.53)Cr_(0.03)N; to 950 deg C for Ti_(0.04)Al_(0.53)Cr_(0.03)N. Machining experiments conducted at the meso and micro scales indicated that cutting tool life is improved significantly using yttrium-doped titanium-based coatings when machining M2 tool steel.