Multilayer Coated Tool Research Articles

Wear mechanisms of WC coated and uncoated tools in finish turning of Inconel 718

This paper presents the results of an experimental investigation on the wear mechanisms of uncoated tungsten carbide (WC) and coated tools (single-layer (TiAlN) PVD, and triple-layer (TiCN/Al 2O 3/TiN) CVD) in oblique finish turning of Inconel 718. Tool wear rate and wear mechanisms were evaluated for cutting speeds, 50< V<100 m/min, and feed rates, 0.075< f<0.125 mm/rev, at a constant depth of cut of 0.25 mm. It was concluded that abrasive and adhesive wear were the most dominant wear mechanisms, controlling the deterioration and final failure of the WC tools. While the triple layer CVD coated tools exhibited the highest wear resistance at high cutting speeds and low feeds, uncoated tools outperformed the single and multi-layer coated tools in the low range of cutting speeds and intermediate feeds. The cutting tool with single-layer PVD coating outperformed the other tools at the medium cutting speed.

Crater Wear Evolution in Multilayer Coated Carbides During Machining Using Confocal Microscopy

Steady-state turning experiments were carried out with multilayer coated inserts consisting of TiN/Al 2O 3/TiCN deposited on a carbide substrate. Confocal microscopy was used for the first time to observe the topography of crater wear evolution in multilayer coated inserts. A hump made of TiN coating next to a growing crater of Al 2O 3, traces of attached steel, and the maximum depth regions have been identified. Scoring marks were also detected in the TiN layer, indicating the presence of abrasion wear. Interestingly, the crater depth was stagnant once it reached the Al 2O 3 layer, and the wear progresses by broadening the area of exposed Al 2O 3. It was concluded that the effectiveness of multilayer coated tools comes from the dissolution resistance of the Al 2O 3 layer, which delays depth growth and develops the wear front into a wider area. Confocal microsocopy was found to be a valuable tool to obtain wear topography for multilayer coated tools.

Characterization of chemical vapor deposited HfN multilayer coatings on cemented carbide cutting tools

The present study has been carried out in order to evaluate the tribological behavior of HfN-based multilayer-coated tools used for milling. The initial results of the wear behavior of multilayer HfN coatings, during the laboratory friction and wear tests conducted at room temperature against WC as tribological pair, are reported. As part of the characterization of the mechanical properties of the coatings, Vickers microindentation tests were also carried out employing loads in the range of 0.01–10 N, in order to evaluate the composite hardness of the coating-substrate systems. Information regarding the absolute hardness of the HfN and TiCN monolayer films has been obtained employing a model recently developed by one of the authors. This information is then used in order to determine the properties of the HfN/TiCN multilayer coating. It has been found that the wear volume of the single layer HfN coatings is approximately 15 times greater than the wear volume corresponding to the HfN/TiCN for the same amount of cycles.

Surface Properties and Performance of Multilayer Coated Tools in Turning Inconel

Nanostructured coatings were developed in order to machine nickel-based super-alloys in Minimum Quantity Lubrication (MQL), or dry conditions. Three dedicated coatings, TiN+AITiN, TiN+AITiN+MoS2 and CrN+CrN:C+C, applied by PVD on WC-Co inserts, developed nanostructured layers exhibiting superior performance, as confirmed by laboratory tests and machining experiments. Coatings surface qualification included, among other tests, SEM observation with EDS analysis, nanoindentation and scratch tests, classic tribological evaluation by ball-on-disk set-up, surface texture analysis. Dry and MQL turning experiments show substantial agreement with tribological and adhesion/toughness tests.

A New Approach to Cutting Temperature Prediction Considering the Thermal Constriction Phenomenon in Multi-layer Coated Tools

A novel approach to the prediction of cutting temperature in multi-layer coated tools is presented. This approach considers the contact mechanics at asperity level and resulting thermal constriction resistance phenomenon. Micro-contact model was developed and the correlation between contact pressure and thermal constriction resistance of uncoated and multi-layer coated tools is established. The thermal interaction and redistribution of heat between the workpiece, the chip and the tool were analyzed, supported by FE model, which considers thermal characteristics of multi-layer coating. The results indicate that the tool coating may cause significant reduction in heat flowing into the tool.