Study On The Tribological Behaviours And Milling Performances Of TiAlN Coating

Comparing to TiN coating, TiAlN coating which extensively applied in the fields of cutting tools and anti-wear components possessed more improved properties, such as hardness, anti-wear, anti-oxidation and adhesion to the substrate materials. In this paper, the tribological behaviors of reciprocating sliding of TiAlN coating which deposited on the cemented carbide substrate were systematically investigated. And the possibility of replacing the cutting tests by reciprocating sliding tests in laboratory has been discussed, which had a great significance for tool enterprise to develop new coatings and relative products quickly, effectively and economically.In this works, the reciprocating sliding tests of ion plating TiAlN coatings and cement carbide substrate have been carried out under different media (in air, emulsion and coolant oil) and varied test parameters (normal loads and displacement amplitudes). In addition, face-milling tests have been carried out in 35CrMoSiV alloy steel using PVD TiAlN coating carbide milling-tool and uncoated fine grain carbide tool, under different feeds and rotational speeds. Optical microscopy (OM), surface profilometer, laser confocual scanning microsopy (LCSM), scanning electron microscopy (SEM), and electron energy spectrum (EDS) have been performed to evaluate the wear scars. The main research results are as follows:1. The variations of friction coefficients of TiAlN coating and cement carbide substrate were classified in five stages. The friction coefficients of the coating were relatively lower than that of the substrate in initial stages, and took more cycles to reach maximal peak value. The friction coefficients of the coating were reduced with the increase of the normal loads, and no obvious effect on the changes of displacement amplitudes can be observed.2. The depths of wear scars of the TiAlN coating and cement carbide substrate increased with the increase of the normal loads and displacement amplitudes. The damage mechanisms of the coating under the condition of reciprocating sliding wear were the combination of abrasive wear, oxidation wear and Delamination.3. The TiAlN coating has obviously improved the cutting performance ofcarbide tools to avoid tipping in initial wear stage, reduce flank wear, and greatly improve the quality of the surface of the workpieces. During the processes of milling 35CrMoSiV alloy steel, the wear mechanism of the TiAIN coating tools was the combination of adhesive wear, delamination and oxidation wear. In the zone of normal working, it was good for alleviating the effect of adhesion and improving working efficiency and the quality of the surface of the workpieces through increasing the rotational speed and feed.4. Under the condition of lubrication of emulsion and coolant oil, the tribological properties of the TiAIN coating were improved evidently. And the lubrication of coolant oil presented the best effect. The TiAIN coating tools enhanced cutting performance obviously by reducing the flank wear in the cutting medium of coolant oil.As a summary, it was very coherent in the experimental results between the cutting test at field and the reciprocating sliding tests in laboratory. It indicated that the reciprocating sliding tests can be used to characterize the cutting performance of tools qualitatively.