Friction and wear behaviors of AlTiCrN coatings by cathodic arc ion plating at high temperatures
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An AlTiCrN coating was prepared on a YT14 cutting tool, whose friction and wear behaviors were investigated with a wear test at 900 and 1000 °C, respectively. The results show that the phases of the AlTiCrN coating mainly are composed of AlN, CrN, and TiN. The elements of Al, Ti, Cr, and N in the coating show gradient and transition distributions at the bonding interface; the C atoms of the substrate have diffused into the lattices of TiN, AlN, and CrN to form the obvious interdiffusion layer; and the interface bonding strength is 57.65 N. The coating is composed of different metal oxides and compound oxides at 900 and 1000 °C. The worn surface is relatively smooth at 900 °C, whose average coefficient of friction (COF) is 0.42, while the worn surface produces severe plastic deformation at 1000 °C, whose average COF is 0.45. There are enriched and depleted stripes with uniformly distributed chemical elements on the worn scar, which is expressed with uniform wear at the high temperatures.
I. INTRODUCTION
With the development of high-speed cutting, dry and semidry cutting technology, the cutting tools with better performances are required, and the cemented carbide and high-speed steel cutting tool substrate coated with a layer of coating makes the coated cutting tools have higher hardness, wear resistance, and oxidation resistance than the original tools, and the coating would improve service life of the cutting tool effectively. TiN, as the first generation of tool nitride coating, is golden yellow with a hardness of 2300 HV, whose coefficient of friction (COF) reaches 0.45–0.52 under the highest working temperature of 500 °C, and can be used for general metal cutting.1 TiAlN coating based on doping TiN coating by aluminum is the second generation of tool nitride coating with a hardness of 3400–3500 HV, whose COF against a quenched steel ball is about 0.5, and the highest working temperature is 800 °C. Because the atomic radius of Al is smaller than that of Ti, Al atoms exist in TiAlN in the form of replacing Ti atoms in TiN; the lattice distortion not only improves the hardness of TiAlN coating but also intensifies adhesive wear of the cutting tool, reducing the workpiece surface accuracy, which is not suitable for precision machining.2,3 To further improve the wear properties of TiAlN coating at high temperatures, Cr element is added into TiAlN coating to form AlTiCrN coating, which belongs to the third generation tool nitride coating. The addition of Cr atoms change a part of the Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.403 J. Mater. Res., Vol. 30, No. 4, Feb 28, 2015
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original hexagonal close-packed (Al, Ti)N phase into a harder cubic (Al, Cr)N phase, improving the wear and oxidation resistance of the coating with hardness of 3400–3600 HV, whose COF at room temperature against a ceramic ball is only 0.4. Due to the formation of stable dense a-(Al, Cr)2O3 when the coating w
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