| Titanium and its alloys possess high specific strength and superior resistance to corrosion making these materials suitable for avariety of applications, such as aerospace, biomedical engineering, architecture and machinery industry. However, titanium and its alloys are difficult to machine because of their high chemical reactivity, low thermal conductivity and relatively low modulus of elasticity. Tools for cutting titanium and its alloys are subject to very serious abrasive, adhesive and thermal loads. Rapid tool wear encountered in machining of these materials is a serious problem. According to the characteristics of titanium alloy processing, the CrAIN and Ti (Cr, Al) SiC (O) N coatings are choose as the research object in this paper in order to confirm their potential application on titanium and its alloy cutting tools.In this paper, The CrAIN films was successful fabricated on cemented carbide alloy (WC-Co) by a duplex treatment of deposition of CrAl coatings followed by plasma nitriding. The micro-structure, mechanical properties and tribological behaviors of CrAIN coatings with different Al content were compared. The results indicated that the content of Al atoms was influenced by deposition parameters of the CrAl coatings. The content of Al atoms was increased with the decreasing of the Cr target current and the increasing of the distance between Cr target and substrate. The main phase composition of CrAIN coatings was nitrides and metal alloy phase (or metal phase). With the increase of the Al atom content, the hardness and elastic modulus of the CrAIN coatings increased, and the coefficient of friction and volume wear rate reduced.The TiSiCN, TiSiCON, TiAlSiCN, TiAlSiCON, TiCrSiCN, TiCrSiCON, CrSiCN, CrSiCON, CrAlSiCN and CrAlSiCON coatings were deposited on cemented carbide substrate using plasma enhanced magnetron sputtering method. The X-ray diffraction, hardness testing, scratch testing, friction and wear test were used to study the effect of metallic elements and oxygen elements on coating properties. The results indicated that most of the oxygen-free coatings had smooth surface with fine grains while the grains of oxygen-coatining coatings were much larger.The main phase composition of oxygen-free coatings and oxygen-coatining coatings were nitrides and carbides.The addition of Ti (or Cr) element to coatings increased their hardness and critical load (Lc) but Al element reduced hardness and Lc value of coatings. Compared to oxygen-containings, oxygen-free coatings had lower Lc values but better resistance of interface crack propagation between film and subustrate and higher hardness values. Combined with the analysis of coefficient of friction, volume wear rate of coatings and TC4, the TiSiCN coating had better wear resistance performance than the CrSiCN coating. The addition of Ti (or Cr) element to coatings enhanced coating wear resistance while Al element reduced wear resistance of coatings. In the Ti based coating, the wear resistance of oxygen-free coatings was better than oxygen-containing coatings. However, in the Cr based coatings, the wear resistance of oxygen-containing coatings was better than oxygen-free coatings.The TiSiCN, TiSiCON, TiCrSiCN, TiCrSiCON, CrSiCN and CrSiCON coatings were also deposited on milling cutter with cemented carbide substrate using plasma enhanced magnetron sputtering method, and the titanium alloy milling experiments were carried out using CNC lathe. The results showed that the temperature of all coated milling cutters was higher than no coated one after milling test. The Cr based coatings had higher temperature than the Ti based coatings. Different coatings on milling cutter had no significant effect on the morphology of scraps. The flank wear of oxygen-free coatings was small and most of the coatings kept great after milling test. But for the oxygen-containings, the detachment was observed and the flank wear of tools was large. |
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