Improvement of PVD coated inserts cutting performance, through appropriate mechanical treatments of substrate and coating surface (original) (raw)
Related papers
Surface and Coatings Technology, 2006
In this work, we investigated the feasibility of increasing the cutting performance of coated tools through the application of multilayered PVD film structures. A monolayer TiAlN and a multilayer TiN/TiAlN coating of the same overall thickness deposited on K35 cemented carbide inserts, were investigated concerning their mechanical, adhesion properties and wear behavior in milling operations. The mechanical properties of both applied films were determined with the aid of nanoindentations and then the evaluation of the corresponding results by appropriate FEM supported algorithms. Impact tests were also conducted to determine film fatigue and adhesion data and the film failure development after the coating fracture initiation. Based on a FEM simulation and on experimental results, the stress field in the cutting wedge region was calculated and the wear initiation and propagation in the investigated mono and multilayer coating cases was explained.
Surface and Coatings Technology, 2003
The fatigue and wear behavior of PVD coatings on cemented carbide substrates in milling are investigated experimentally and Ž . analytically through Finite Elements Method FEM simulation of the cutting process. Cutting inserts with different cutting edge radii and at various feedrates were examined. The initiation and progress of the tool failure is depicted through Scanning Ž . Electron Microscopy SEM and Energy Dispersive X-ray microspectral investigations of the used cutting edges. The FEM simulation of the contact between the tool and the workpiece enables a quantitative description of the influence of mechanical stress components on the coating fatigue failure. Hereby critical coating fatigue stresses determined by means of the impact test were considered. The experimental and computational results exhibit quantitatively the effect of tool radius and feed rate on the coating fatigue failure as well as on the overall cutting performance for various substrates and film structures. In order to utilize the superior characteristics of coatings towards improving the cutting performance, it is highly recommended to optimize the cutting insert wedge radius, as well as the cutting conditions. Herewith a premature coating failure and a consequent rapid wear development can be prevented. ᮊ
Surface & Coatings Technology, 2004
The film deposition conditions on individual specimens in the vacuum chamber during a physical vapour deposition coating procedure cannot be considered as constant. Depending among others on the magnetic field distribution in the vacuum chamber as well as on the specimen fixture geometry and kinematics, the coating hardness and mechanical properties may vary. In order to investigate the effect of coating hardness and strength on the cutting performance in milling, (Ti Al )N films having thickness 46 54 from 3 to 10 mm and varying hardness were deposited on cemented carbides inserts. The coating material properties and especially their stress-strain laws were determined from the nanoindentation measurement results using a finite elements method (FEM) based evaluation procedure. The initiation and progress of the coating and tool wear in milling were studied using scanning electron microscopy and energy dispersive X-ray spectroscopy. The investigations revealed that as the coating grows thicker, its superficial hardness and strength decreases. For the thick coatings, however, this does not affect the cutting performance as much as for the thin coatings. In the case of thin coatings, a corresponding decrease of the film hardness and strength, diminishes significantly the cutting performance. A FEM simulation of the cutting process, whereas the coating mechanical properties vs. the film thickness are considered, elucidates the aforementioned results. ᮊ
CIRP Annals - Manufacturing Technology, 2002
The fatigue and wear behaviour of PVD coatings on cemented carbide inserts with various cutting edge radii are investigated experimentally and analytically in milling. The inserts with cutting edge radii from 8 up to 35 µm were manufactured by honing and micro-blasting. The tool wear progress was depicted through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) microspectral analysis. The Finite Elements Method (FEM) simulation of the contact between the tool and the workpiece highlights the effect of the cutting edge radius on the first coating fracture and the further wear development. The wear behaviour of the cutting edge radii manufactured by honing, in comparison to the corresponding ones by means of micro-blasting, is significantly enhanced, whereas the cutting edge radius increasing can lead to a higher tool life.
WEAR OF PVD COATED TOOLS IN MILLING AFFECTED BY THE GRAIN SIZE OF CEMENTED CARBIDE SUBSTRATES
To explain the coating and substrate wear behaviour, when applying cemented car- bide (HM) tools with different grain sizes in milling, two variations of HM inserts, a fine- and an ultra-fine-grained one were coated with the same PVD AlTiN film. These inserts were examined by nanoindentations and impact tests concerning me- chanical properties and by milling experiments regarding wear. The investigations revealed an enhanced cutting performance of the less hard and more ductile fine- grained substrate compared to the ultra-fine-grained one. In turn, the coating depos- ited on the ultra-fine-grained insert showed increased mechanical properties and impact resistance, compared to the corresponding one deposited on the fine-grained substrate. Moreover, an improved cutting performance was obtained in the latter case at a width of flank wear land less than 0.1 mm. At greater flank wear values, the fine-grained substrate withstands more effective the cutting loads, due to its bet- ter duc...
2005
This paper investigates the feasibility of increasing the wear resistance of cemented carbide tools through micro-blasting of their PVD coatings. The enhanced and graded film strength properties before and after micro-blasting are determined by means of an FEM-based evaluation of nanoindentation results. The coating topomorphy induced by micro-blasting was monitored and correlated to the substrate roughness and film adhesion. The cutting performance of inserts coated with micro-blasted films was investigated in milling and explained with the aid of a cutting process FEM simulation. The obtained results reveal a tool life growth through micro-blasting of coatings, deposited on substrates with appropriate roughness characteristics. D
EFFECT OF THE CUTTING EDGE SHAPE ON THE PERFORMANCE OF COATED CEMENTED CARBIDED INSERTS
In the present paper, the effect of the coated cutting edge shape on the tool milling performance is described. According to the actual cutting edge profile, three groups of coated cemented carbides inserts with an AlTiN PVD film without treatment (as dep.) as well as with slight (S.G.) or intensive (I.G.) cutting edge rounding were ex- amined. The cutting edge geometry was determined by confocal white light scan- ning, while the film thickness on the tool flank and rake were registered, by micro cratering tests combined with confocal measurements. The impact resistance and corresponding fatigue properties versus the impact temperature were detected by impact tests. The cutting performance of the inserts of the various groups, was in- vestigated in peripheral milling, of hardened steel 42CrMo4 QT. The obtained re- sults were explained by FEM calculations of the material removal process enabling the determination of the developed stresses and temperature distributions in the cut- tin...
… Department, Aristoteles …, 2000
The evolution of the Physical Vapour Deposition (PVD) method as a thin film production technique enabled the broad diffusion of thin hard coatings also in manufacturing technology. Coated tools may reach a cutting accomplishment of ten -up to one hundred times greater than the corresponding of the same uncoated ones under the same cutting conditions. However, despite this performance of modern coated systems, thin films experience a variety of failure mechanisms during their operation, which is strongly dependent on the manufacturing case and the cutting conditions. This wide application of thin hard PVD coatings under severe dynamic stress states on cutting tools, leads to the need of the precise knowledge of coating mechanical properties such as the coating fatigue and static stress limits. In the present paper the coating impact test is applied to determine the fatigue behavior of coating-substrate compounds in a form of generally applicable diagrams. The failure mechanisms of coatings are also examined and interpreted in milling, offering an overview of the operational limits of coated tools. In order to utilize the superior characteristics of coatings towards improving the cutting performance, it is highly recommended to optimize the cutting insert wedge radius, as well as the feedrate and the cutting speed. Herewith a premature coating failure and a consequent rapid wear development can be prevented.
Adhesion is one of the most important characteristics of coating on cutting tools. Poor coating adhesion on the tool favors fragmentation and release of hard abrasive particles between the tool and the work-piece. These particles interact with the surfaces of the tool, accelerating its wear and decreasing tool life. One possible solution is the use of laser texturing prior to coating in order to achieve a desired surface topography with enhanced adhesion properties. In the texturing, a high-frequency short-pulse laser changes surface characteristics, generating resolidified material and selective vaporization. This work evaluated the effectiveness of laser texturing in improving the substrate–coating adhesion of PVD coated cemented carbide tools. To this end, the substrates were textured with a Nd:YAG laser, in four different intensities, and then coated with a PVD TiAlN film. To ascertain the effectiveness of laser texturing, Rock-well C indentation and turning experiments were performed on both textured tools and conventional unlasered tools. The PVD coated laser-textured tool showed better performance in the indentation and turning tests than the standard tools. A comparative evaluation of tool wear mechanisms indicated that texturing did not change the wear mechanisms, but altered their importance to tool wear. The anchoring provided by the higher roughness of the textured surface increased the adhesion of the coating on the substrate, thus increasing tool life. Additionally, the chemical modification of the carbide grains due to the laser heating might be responsible for an enhanced adhesion between coating and substrate.
Increasing tool life by adjusting the milling cutting conditions according to PVD films’ properties
CIRP Annals - Manufacturing Technology, 2008
The coated tools cutting performance in up and down milling depends significantly on the PVD film material properties. The related wear mechanisms at various cutting speeds can be sufficiently explained considering the developed tool loads and the non-linear coating impact resistance versus temperature. Various PVD coated cemented carbide inserts were tested at different cutting conditions. The corresponding cutting loads and temperatures were determined by FEM simulations and the films' impact resistance by impact tests. A correlation between the impact resistance and the cutting performance at corresponding temperatures contributed to the optimum adjustment of the cutting parameters to the film properties.