Abstract
In this study, three kinds of coatings, AlTiN, AlTiN–Ni, and AlTiN–Cu were deposited via the cathodic arc evaporation method. The microstructure, mechanical properties, oxidation resistance, and cutting behavior of these coatings were then investigated. The incorporation of Cu(Ni) into AlTiN eliminated its columnar structure and led to an increase in the growth defects of its macroparticles. The addition of Cu and Ni decreased the hardness of the coatings, their elastic moduli, and their friction coefficients. All of the AlTiN, AlTiN–Ni, and AlTiN–Cu coatings presented sufficient adhesion strength values. The oxidation resistance of these three coatings was determined to be in the following order: AlTiN > AlTiN–Ni > AlTiN–Cu. Titanium turning experiments indicated that the cutting force was reduced and the tool life was improved through doping with Cu(Ni) elements, dependent on cutting speed. The AlTiN–Ni coating showed the best performance at a high cutting speed, whereas the AlTiN–Cu coating was more successful at a lower cutting speed.
Highlights
Titanium is difficult to machine for many reasons
The AlTiN, AlTiN–Ni, and AlTiN–Cu coatings were deposited on a cemented carbide substrate (WC-6 wt.% Co) and polycrystalline Al2 O3 using a cathodic arc evaporation system with Ti0.33 Al0.67, (Ti0.33 Al0.67 )0.985 Ni0.015, and (Ti0.33 Al0.67 )0.97 Cu0.03 powder metallurgy targets, respectively
The slightly lower adhesion strength of the AlTiN–Ni and AlTiN–Cu coatings can be attributed to their higher MP contents, which results in decreased surface roughness [27]
Summary
Titanium is difficult to machine for many reasons. Its low thermal conductivity creates extremely high temperatures at the tool-chip interface, its high chemical affinity results in severe adhesion to cutting tools, and its high plasticity and toughness give rise to poor cutting stability [1,2,3,4,5]. TiAlN coatings prepared by conventional methods often exhibit a columnar structure and have a high friction coefficient. These properties make them susceptible to cracks and severe adhesion wear during the machining of Ti [9,10]. Blov et al found that TiAlN coatings doped with Cu and Ni exhibit excellent cutting performance during both the continuous and intermittent turning of steel [15] Another effective method involves improving the oxidation. A single-phase cubic TiAlN coating with a high Al content (referred to as AlTiN) has been shown to exhibit excellent mechanical properties and oxidation resistance. The mechanism of Cu(Ni)-action on the oxidation resistance and titanium cutting behavior of AlTiN coatings was explored
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