Papers by Keyword: PVD Coating

Abstract: The use of cutting fluids in turning can change thermomechanical loading of cutting tools. Currently, manufacturers provide a wide range of cutting fluids, which have different combinations of lubricating and cooling properties. Depending on cutting conditions, this combination can reduce tool wear in different degrees, and, in some cases, to even increase it. Therefore, an effective choice of cutting fluids requires a considerable amount of experiments, which requires cost and time. To solve this problem in the software SIMULIA/Abaqus Explicit 6.10 was developed thermomechanical model of the turning process by cutting tools with PVD-coating, which allows simulating the effect of any combination of cooling and lubricating action. An Arbitrary Lagrangian-Eulerian formulation method was used in the modeling. Under the lubricating and cooling action is understood the final result of interaction of cutting fluids with the cutting zone. Modeling of lubricating action of cutting fluid is performed by introducing into the model corresponding average coefficient of friction in the contact zone of cutting tool, worked material and cutting fluid. Modeling of cooling action of cutting fluids is implemented through the introduction of the heat transfer coefficient, calculated on the basis of cutting conditions and thermo-physical properties of cutting fluids. As an example, turning of austenitic stainless steel X10CrNiTi18 by carbide cutting insert with TiN-coating for a predetermined cutting condition was examined. A selection of cutting fluids of the proposed range, formulations of which have different combinations of cooling and lubricating properties ("Unizor-M", "Ferrobetol-M", "EkoEM-1", "STARCUT E9", "SAFECUT M120") was accomplished through the simulation model and the calculated data contact stresses. Experimental studies have confirmed the validity of this choice by comparing the rate of flank tool wear in the using different cutting fluids. The rate of wear was determined by surface micrographs of flank tool. An application of the recommended cutting fluid "SAFECUT M120" has reduced wear by 4 times as compared with the application of the "Ferrobetol-M", the use of which has shown the highest wear. The model developed can be used for selecting a predetermined range of cutting fluids, in determining the optimal combination of lubricating and cooling actions for establishing the required characteristics of cutting fluid or in developing new formulations of cutting fluids.

Abstract: In the present article, the laser hardening of the carbon steel C45, previously coated by the physical vapour deposition (PVD) process, is studied. The (Al,Ti)N-G and nACo® (nc-Al_xTi_1-xN/α-Si₃N₄) coatings were applied. Nd:YAG laser with the laser beam power density of 1945 W/cm² and scan speed of 300 mm/min was used for hardening process. Laser hardening lead to the formation of hardened layer under both coatings, consisting of austenite and ferrite. The approximate depth of the hardened layer and maximal microhardness was approximately 0.2 mm and 955 HV0.05 and 0.1 mm and 520 HV0.05 in the case of the (Al,Ti)N-G and the nACo® coating, respectively. After laser hardening the sliding wear of the (Al,Ti)N-G coating decreased by 1.25 times and of the nACo® coating by 1.05 times.

Abstract: The duplex treatment consisted of a plasma nitriding at 470 °C for 4 h and subsequent coating with TiN layer was applied on AISI 304L stainless steel. The article is concerned to a study of the chemical composition and mechanical properties of duplex system. GDOES method, laser confocal microscopy, nanohardness and indentation test were employed to characterize the chemical composition, depth profiles, surface morphology, hardness, adhesion. The results show that the duplex surface system possesses a desirable combination of properties especially hardness. Adhesion of PVD coating was increased on nitrided surface.

Abstract: This work proposes the investigation of nanosized Titanium Aluminum Nitride (TiAlN) on the Stainless Steel (316L) substrate. A chromium interlayer has been applied over the modified surface which will act as an interlayer between the substrate and hard composite coating. The composite coating was prepared by Magnetron Sputtered-Physical Vapour Deposition (PVD) on chromium coated lapped and textured surfaces of stainless steel substrate. Scratch test was performed to characterize the adherence of the coatings on the substrate. TiAlN surface coating over the textured surface exhibits higher adherence than the lapped surface coating surface. The tribological performance of the wear resistant coatings on lapped and textured surfaces was experimentally investigated by pin on disc tribometer at dry sliding contact conditions under various normal loads. The testing results were compared and the results showed that TiAlN coating on textured surfaces exhibited lower friction coefficient and wear rate than lapped coating surfaces under same testing conditions. Sliding wear characteristics such as coefficient of friction and specific wear rate were investigated.

Abstract: The use of PVD and CVD coatings has increased significantly thanks to the improved tribological performances they offer in many metalforming processes. Nevertheless the proper coating selection for a specific forming operation is not well established yet, being mainly based on trails and error approaches. The use of FEM-supported analyses may represent an effective support in the optimization of process parameters, but the need of testing procedures and reliable models to describe the mechanical and tribological phenomena at the interface between the dies and the workpiece is still significant. The paper presents a novel experimental set-up for the evaluation of the wear resistance of dies coatings in sheet metal forming operations. A progressive stamping process was taken as reference case and analyzed by numerical analyses. Contact pressures, temperatures and tangential loads at the tools-blank interface were evaluated in each deformation step. TiAlN and CrN were selected as reference coatings and deposited via magnetron sputtering technique. The first part of the research was focused on the design of the novel set-up capable to carry out controlled wear tests in laboratory environment, performed with the parameters obtained from the numerical simulation. The results of such experiments were compared to the ones from standard laboratory tests and with industrial trials, though measurements of loads, of surface roughness evolution and by surface investigations trough Scanning Electron Microscope observations.

Abstract: Surface roughness is an important output in different manufacturing processes. Its characteristic affects directly the performance of mechanical components and the fabrication cost. In this current work, an experimental investigation was conducted to determine the effects of various cutting speeds and feed rates on surface roughness in turning the untreated and Sb-treated Al-11%Si alloys. Experimental trials carried out using PVD TIN coated inserts. Experiments accomplished under oblique dry cutting when three different cutting speeds have been used at 70, 130 and 250 m/min with feed rates of 0.05, 0.1 and 0.15 mm/rev, whereas depth of cut kept constant at 0.05 mm. The results showed that Sb-treated Al-11%Si alloys have poor surface roughness in comparison to untreated Al-11%Si alloy. The surface roughness values reduce with cutting speed increment from 70 m/min to 250 m/min. Also, the surface finish deteriorated with increase in feed rate from 0.5 mm/rev to 0.15 mm/rev.

Abstract: One of the important aspects of machining is the measurement of the cutting forces acting on the tool. The information of forces is required for evaluation of power requirements, designing tool holder, machine tool elements and fixture. In this research, the effect of cutting condition on cutting force when turning untreated Al-11%Si-1.8%Cu and Sb-treated alloys was investigated. PVD TiN coated insert as cutting tool under oblique dry cutting process utilized. Experiments were conducted at three different cutting speeds of 70, 130 and 250 m/min with feed rates of 0.05, 0.1 and 0.15 mm/rev, whereas depth of cut was kept constant at 0.05 mm. The results revealed that turning of Sb-treated alloys requires higher cutting force in comparison to untreated alloy. The cutting force values increased about four times with increasing feed rate from 0.05 mm/rev to 0.15 mm/rev. Furthermore, the cutting force decreased with increasing cutting speed from 70 m/min to 250 m/min.

Abstract: Cutting tool material technology in recent years has made great strides with substantial improvements in their strength, toughness, and wears resistance, which are designed to increase productivity, improve tool selection and aid to decrease costs and promote machining quality. This investigation presents the effect of various cutting speeds in turning of Al6061 with respect to different coatings. Experiments carried out under orthogonal dry cutting, and two different cutting speeds applied which were 250, 500 m/min. Feed rate and depth of cut kept constant respectively at 0.05 mm/rev and 0.5 mm in experiments. Three different carbide cutting tools have been used namely CVD tri-phase multilayer TiC/TiCN/TiN coated, PVD TiN coated and CVD TiC/Al2O3 coated. Tool performance was determined with respect to tool wear and surface finish in tests. Results obtained that tri-phase coated illustrated longest tool life, however best surface finish achieved by TiN coated tool. In addition adhered material which mainly formed in CVD tri-phase TiC/TiCN/TiN and TiC/Al2O3 coated tools, at higher cutting speed deteriorated surface finish in comparison to lower cutting speed.

Abstract: The results of an investigation on the effects of surface roughness on ball end mill are reported here. We used grindwheels with varying in grit between #325 and #1000 to grind ball end mill’s rake surface and flank surface, and then coated the end mill with TiAlN film, CrSiN film, and TiSiN film. We measured the state of adhesion on the films on the rake surface in continuous lathe milling as well as the surface roughness and cutting force. The results show that, in generating the cutting cutoff, the optimum grinding roughness differs between the near vicinity of the cutting-edge ridgeline and the part of the rake surface that is further away from the cutting-edge ridgeline. From that fact, we understand that the cutting characteristics of the work material and the surface area of the rake surface that is in contact with the cutting cutoff exert their respective influences during the cutting.

Abstract: In the present study laser nitriding of titanium alloy surface is carried out and fracture toughness of the resulting surface is measured using the micro-indentation method. The fracture toughness is then related to the microstructure of the laser treated surface. It is found that laser gas assisted nitriding lowers the fracture toughness of the surface due to the micro-stress formed at the surface region during the high cooling rates.