Search Results (30)

Ultra-high-temperature ceramic (UHTC) coatings offer a promising route to extending cutting tool service life under severe conditions. This work evaluates the tribological behaviour and wear regime transitions of ZrB₂–SiC/ZrO₂ coatings, deposited by physical vapour deposition (PVD) onto ASSAB-17 high-speed steel tool bits, during dry turning of Ti-6Al-4V. Structural, microstructural, mechanical, and tribological characterisation was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation, and pin-on-disc testing under three pressure–velocity (PV) severity levels, with worn surfaces analysed by SEM and profilometry. The coating exhibited a nanostructured ZrB₂/β-SiC/t-ZrO₂ architecture with a hardness (H) of 24 ± 3 GPa, a hardness-to-reduced-elastic-modulus ratio (H/Er) of 0.100, and an elastic resistance to plastic deformation (H³/Er²) of 0.240 GPa. Three tribological regimes were identified: running-in, steady-state sliding, and progressive degradation, with the highest severity (PV = 6.0 N·m/s) triggering degradation beyond approximately 620 m, a more than one-order-of-magnitude rise in wear rate, and the only case exceeding the tool-life criterion of maximum flank wear (VBmax = 0.30 mm) according to ISO 3685. The main advantage of the proposed approach is that it condenses tool-life-relevant behaviour into a single, easily measurable severity parameter, the PV product, directly applicable to coating design and the selection of safe machining-condition windows. The overall behaviour is consistent with a mechanism governed by the stability and regeneration capacity of a protective tribofilm. As the composition of this layer was not directly characterised, this mechanism is proposed as a phenomenological interpretation, from which a PV threshold is derived as a design criterion for UHTC coatings. Full article

Recently, there has been growing interest in the synthesis of thin films made from metal diboride. Boron forms binary compounds with a wide variety of metals. These diborides are refractory, ultra-hard solids characterized by high melting points, exceptional thermal stability, and pronounced chemical inertness. This work describes the preparation of metal diboride coatings made of binary ZrHfB₂, HfTiB₂ and ZrTiB₂ as well as ternary HfZrTiB₂. In the low-pressure chemical vapor deposition (LPCVD) process used, MeCl₄ (Me = Zr, Hf, Ti), BCl₃, H₂, and Ar were employed at deposition temperatures of 850 °C. The coatings were characterized with respect to phase composition, crystal structure, hardness, residual stress and wear behavior. A hardness of 38 GPa was achieved with a modulus of elasticity of around 700 GPa and a moderate tensile residual stress of approx. 400 MPa was obtained for the ternary alloys as well as 44 to 633 MPa for the binary alloys, respectively. The phase composition and structure of the deposited layers were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The investigations revealed dense, crack-free, well defined crystalline single-phase diboride layers with grain sizes of 0.1–1.5 µm. A TiN interlayer applied prior to diboride deposition significantly enhanced adhesion between the diboride coating and hard-metal inserts. Scratch test measurements revealed critical loads of approximately 90 N. In the wear test milling against TiAl6V4, the HfZrTiB₂ coating (with ZrCl₄:HfCl₄:TiCl₄ = 1:2:1) demonstrated the best tool life with ~15% improvement over the state-of-the-art CVD TiB₂ reference coating using a single cutting condition. The tool life for the ZrTiB₂ coating was 20% below the tool life of the reference coating. Full article

Suitable nitride coating deposition could improve the wear resistance of WC/Co carbide tools when cutting Ti₂AlNb typical difficult-to-machine alloy. However, there is no clear conclusion on which nitride series coating is suitable for improving the friction characteristics between WC/Co carbide and Ti₂AlNb alloy. In this research, the CrAlN, CrAlN/(CrAlB)N/CrAlN, and TiAlN/ZrN coatings were deposited on WC/Co carbide with the only variable of coating type, which were utilized to conduct the high-temperature pin disc experiments with Ti₂AlNb alloy at 600 °C, respectively. The high-temperature friction characteristics were analyzed by the friction coefficient with time, the alloy wear rate, the surface morphology, and element distribution after wear. The results showed that the three types of coating all improved the high temperature friction and wear characteristics of WC/Co carbide. The Ti₂AlNb alloy also exhibited good surface morphology after wear with TiAlN/ZrN-coated carbide. It is speculated that TiAlN/ZrN coating was the suitable coating deposition on WC/Co carbide tools to improve cutting performance of Ti₂AlNb alloy. Full article

Drilling-induced damage in fiber-reinforced polymer composite materials was measured excavating four laminates, basalt (B₁₄), glass (G₁₄) and their two sandwich type hybrids (B₄G₆B₄, G₄B₆G₄), with 6 mm twist drills at 1520 revolutions per minute and 0.10 mm rev⁻¹ under dry running with an uncoated high-speed steel (HSS-R), grind-coated high-speed steel (HSS-G) or physical vapor deposition-coated (high-speed steel coated with Titanium Nitride (TiN) and Titanium Aluminum Nitride (TiAlN)) drill bits. The hybrid sheets were deliberately incorporated to clarify how alternating basalt–glass architectures redistribute interlaminar stresses during drilling, while the hard, low-friction TiN and TiAlN ceramic coatings enhance cutting performance by forming a heat-resistant tribological barrier that lowers tool–workpiece adhesion, reduces interface temperature, and thereby suppresses thrust-induced delamination. Replacement of an uncoated, grind-coated, high-speed-steel drill (HSS-G) with the latter coats lowered the mechanical and thermal loads substantially: mean thrust fell from 79–94 N to 24–30 N, and peak workpiece temperatures from 112 °C to 74 °C. Accordingly, entry/exit oversize fell from 2.5–4.7% to under 0.6% and, from the surface, the SEM image displayed clean fiber severance rather than pull-out and matrix smear. By analysis of variance (ANOVA), 92.7% of the variance of thrust and 86.6% of that of temperature could be accounted for by the drill-bit factor, thus confirming that the coatings overwhelm the laminate structure and hybrid stacking simply redistribute, but cannot overcome, the former influence. Regression models and an artificial neural network optimized via meta-heuristic optimization foretold thrust, temperature and delamination with an R² value of 0.94 or higher, providing an instant-screening device with which to explore industrial application. The work reveals TiAlN- and TiN-coated drills as financially competitive alternatives with which to achieve ±1% dimensional accuracy and minimum subsurface damage during multi-material composite machining. Full article

Inconel 617 is a nickel-based superalloy that is a primary candidate for use in next-generation nuclear applications such as the Gen IV Molten Salt Reactor (MSR) and Very-High-Temperature Reactor (VHTR) due to its corrosion and oxidation resistance and high strength in elevated temperatures. However, Inconel 617 machinability is poor due to its hardness and tendency to work harden during manufacturing. While the machinability of its sister grade, Inconel 718, has been widely studied and understood due to its applications in aerospace, there is a lack of knowledge regarding the behaviour of Inconel 617 in machining. To address this gap, this paper investigates the influence of cutting parameters in the turning of Inconel 617 and compares the impact of Minimum Quantity Lubrication (MQL) turning against conventional coolant. This investigation was performed through three distinct studies: Study A compared the performance of commercial coatings, Study B investigated the influence of cutting parameters on the surface finish, and Study C compared the performance of MQL to flood coolant. This work demonstrated that AlTiN coatings performed the best and doubled the tool life of a standard tungsten carbide insert compared to its uncoated form. Additionally, the feed rate had the largest impact on the surface roughness, especially at high feeds, with the best surface quality found at the lowest feed rate of 0.075 mm/rev. The utilization of MQL had mixed results compared to a conventional flood coolant in the machining of Inconel 617. Surface finish was improved as high as 47% under MQL conditions compared to the flood coolant; however, work hardening at the surface was also shown to increase by 10–20%. Understanding this, it is possible that MQL can completely remove the need for a conventional coolant in the machining of Inconel 617 components for the manufacturing of next-generation reactors. Full article

In this study, the drilling of an Al 6082-T6 alloy and the effects of cutting tool coating and cutting parameters on surface roughness, cutting temperature, hole diameter, circularity, and cylindrical variations was investigated. In addition, the prediction accuracy of Taguchi, artificial neural networks (ANNs), and adaptive neuro-fuzzy inference system (ANFIS) methods was compared using both experimental results and Signal/Noise (S/N) ratios derived from the experimental results. The experimental design was prepared according to Taguchi L27 orthogonal indexing. As a result, it was observed that increasing the cutting speed and feed rate increases the cutting temperature hole error, circularity error and cylindricity error. Increasing the cutting speed positively affected the surface roughness, while increasing the feed rate led to an increase in the surface roughness. The lowest surface roughness, cutting temperature, hole diameter error and hole circularity error values were measured for the uncoated cutting tool. The minimum cylindricity variation was measured for drilling with TiAlN-coated cutting tools. The optimum cutting parameters were A1B1C3 (Uncoated, 0.11 mm/rev, 200 m/min) for surface roughness, A1B1C1 (Uncoated, 0.11 mm/rev, 120 m/min) for cutting temperature, hole error, circularity error and cylindricity error. In the estimation of the output parameters with Taguchi, ANNs and ANFIS, it was observed that the estimates made by converting the experimental values into S/N ratios were more accurate than the estimates made with the experimental results. The reliability coefficient and prediction ability of the ANN model were found to be higher than Taguchi and ANFIS models in estimating the output parameters. Full article

This study aims to determine the extent to which coating composition and workpiece properties impact machinability and tool selection when turning Compacted Graphite Iron (CGI) under extreme roughing conditions. Two CGI workpieces, differing in pearlite content and graphite nodularity, were machined at a cutting speed of 180 m/min, feed rate of 0.18 mm/rev, and depth of cut of 3 mm. To assess the impact of tool properties across a wide range of commercially available tools, four diverse multilayered cemented carbide tools were evaluated: Tool A and Tool B with a thin AlTiSiN PVD coating, Tool C with a thick Al₂O₃-TiCN CVD coating, and Tool D with a thin Al₂O₃-TiC PVD coating. The machinability of CGI and wear mechanisms were analyzed using pre-cutting characterization, in-process optical microscopy, and post-test SEM analysis. The results revealed that CGI microstructural variations only affected tool life for Tool A, with a 110% increase in tool life between machining CGI Grade B and Grade A, but that the effects were negligible for all other tools. Tool C had a 250% and 70% longer tool life compared to the next best performance (Tool A) for CGI Grade A and CGI Grade B, respectively. With its thick CVD-coating, Tool C consistently outperformed the others due to its superior protection of the flank face and cutting edge under high-stress conditions. The cutting-induced stresses played a more significant role in the tool wear process than minor differences in workpiece microstructure or tool properties, and a thick CVD coating was most effective in addressing the tool wear effects for the extreme roughing conditions. However, differences in tool life for Tool A showed that tool behavior cannot be predicted based on a single system parameter, even for extreme conditions. Instead, tool properties, workpiece properties, cutting conditions, and their interactions should be considered collectively to evaluate the extent that an individual parameter impacts machinability. This research demonstrates that a comprehensive approach such as this can allow for more effective tool selection and thus lead to significant cost savings and more efficient manufacturing operations. Full article

Nowadays, the application of protective multicomponent coatings based on hard metal nitrides is increasingly used to increase the resistance of structures and tools to wear, corrosion, and oxidation. In the present work, the multicomponent system Ti-Al-Ta-Si-N is studied, which has high hardness and crack resistance combined with thermal stability and oxidation resistance. The process of formation of the nanocrystalline structure of the coating during its deposition on materials plays a key role in the optimization of these properties. The nanocrystalline structure of the coating is formed due to Si impurity, which is poorly soluble in the Ti_1−x−yAl_xTa_yN system based on B1-TiN and segregates mainly along grain boundaries, forming grain boundary amorphous phases of Si_zN type. In order to find the optimal composition of multicomponent coatings with improved physical and mechanical properties, it is necessary to understand the peculiarities of interaction of Si impurity with the surface of B1-TiN phase in the presence of Al and Ta substitutional impurities. In the present work, with the help of first-principles calculations of electronic and atomic structure of (001) and (111) surfaces of the Ti_1−x−yAl_xTa_yN system with adsorbed Si atom and the interatomic bond study apparatus based on the calculation of a crystal orbital Hamilton population and a crystal orbital bond index, the nature of the bonds between adsorbed Si and the N, Ti, Al, and Ta atoms of the Ti_1−x−yAl_xTa_yN surface system has been studied. It was found that the binding energy of Si with the Ti_1−x−yAl_xTa_yN surface system can be both higher and lower than the binding energy of its bonding with the surface of the binary TiN compound depending on the position of the Al and Ta substitution atoms in the surface layers. The Si bonding with the atoms of the Ti_1−x−yAl_xTa_yN surface is ionic–covalent in nature. It is shown that the Si-Ta interaction has the highest degree of covalency and strength, and the Si-Al interaction is predominantly ionic in most cases considered and is weaker than the Si-Ti and Si-N bonds. Impurity atoms of Al or Ta have very little effect on the Si-Ti and Si-N bonds due to the local nature of the bonds in the Ti_1−x−yAl_xTa_yN surface system with adsorbed silicon atoms. Full article

Magnesium alloys are an important group of materials that are used in many industries, primarily due to their low weight. Constantly increasing quality requirements make it necessary to improve the accuracy of manufactured products. In this study, the precision milling process for AZ91D and AZ31B magnesium alloys was investigated, and the results obtained with uncoated and TiB₂-coated end mills were compared. The impact of variable cutting parameters was also investigated. Specifically, the study focused on the dimensional accuracy of the machined parts. The results showed that even though the dimensional accuracy obtained in milling both magnesium alloys was comparable, it was higher in the case of the AZ31B alloy by up to 22%. The study also demonstrated that the use of the TiB₂ coating did not have the desired effect and that higher dimensional accuracy up to 27% was obtained with the uncoated tool. Full article

This paper describes the principles of obtaining wear-resistant coatings based on titanium diboride that are deposited on the cutting tool for use in the machining of chromium–nickel alloys. The spark plasma sintering of samples from the TiB₂/Ti powder composition was studied, and the influence of sintering modes on the characteristics of the ceramic targets was analyzed. The regularities of the magnetron sputtering of sintered targets were revealed. The dependences of the physical and mechanical properties of coatings formed on hard alloy substrates on deposition conditions were established. The wear resistance of carbide samples with TiB₂-based coatings under friction-sliding conditions and coated carbide ball-end mills in milling Inconel 718 chromium–nickel alloy that is widely used in the industry was assessed. Full article

Physical vapor deposition (PVD) coatings could affect the friction performance at the contact interface between Ti₂AlNb alloy parts and tool couples. Suitable coating types could improve the friction properties of Ti₂AlNb alloy while in contact with WC/Co carbide. In this study, the linear reciprocating pin–disc friction tests between the Ti₂AlNb alloy and the WC/Co carbide tool couple, with the sole variation of the PVD CrAlN/(CrAlB)N/CrAlN coating were conducted within the temperature range of 25–600 °C. The antifriction properties of the Ti₂AlNb alloy were estimated using the time-varied friction coefficients, the alloy wear rate, worn surface topography, worn surface element, and wear mechanism analysis. The results showed that the PVD CrAlN/(CrAlB)N/CrAlN coating could decrease the average friction coefficient and alloy wear rate compared to the uncoated WC/Co carbide couple. The apparent adhesive wear and abrasive wear of the Ti₂AlNb alloy could be improved due to the PVD coating at evaluated temperatures. The PVD CrAlN/(CrAlB)N/CrAlN coating could be utilized to improve the antifriction properties of the Ti₂AlNb alloy, which may be deposited on the cutting tool to improve the machining performance of Ti₂AlNb alloys in future aerospace machining industry. Full article

The present research investigated the turning of AZ31B magnesium alloy in a dry environment using carbide tool inserts coated with tungsten carbonitride (TiCn) and thin alumina (Al₂O₃). A Box–Behnken design based on fifteen experiments showed a proportional increasing trend of flank wear with all three machining parameters, i.e., cutting speed, feed rate, and depth of cut. The most influential parameter is the cutting speed. A maximum flank wear of 299.34 µm due to excessive adhesion of work material on the tool face was observed at a high cutting speed. Machining at low speed resulted in a significant reduction in tool wear due to less chipping. The tool wear and chip morphology study confirmed the results. Full article

TiB₂ is a promising material for several fields including impact-resistant armor, wear-resistant coatings, cutting tools and crucibles given its physical, mechanical and chemical properties, especially due to the combination of high hardness and exceptional wear resistance. It is however very difficult to sinter below 2000 °C, even under mechanical pressure; moreover, the low fracture toughness limits the applicability of the ceramic material. By using sintering additives, it is possible to improve the sintering process and increase the mechanical properties since the additives react with oxidized layers and form secondary phases. In this study, different preparation methods and various combinations of additives (B₄C, Si₃N₄ and MoSi₂) via hot pressing sintering have been explored. Through the synergy between optimized process and tailored composition, an almost fully dense material was obtained at 1700 °C with hardness of 24.4 ± 0.2 GPa and fracture toughness of 5.4 ± 0.2 MPa m^1/2. However, the highest hardness (24.5 ± 0.2 GPa) and density values were obtained for only the high-energy-milled sample with WC-Co media, featuring a core–shell grain structure. Finally, optical properties for selected samples were measured, identifying the high-energy-milled TiB₂ as the sample with the highest spectral selectivity α/ε and solar absorptance. Full article

The high-entropy PVD coating (AlCrZrTiTa)N, characterized by its high hardness (50–60 GPa), elastic modulus above 300 MPa, and high heat resistance up to 1300 °C, is used for coating cutting tools operating under extreme metalworking conditions. The nanostructured monolayer 3 μm PVD coating was deposited on cutting plates in the hybrid arc deposition PVD coater. The coating had an amorphous nanocrystalline microstructure with a grain size of about 10–50 nm. The samples of SS 304 steel were investigated during dry high-speed (600 m/min) cutting. Raman spectroscopy was used to study the formation of tribooxides on the tool surface at the running-in stage of the cutting. After 130 m of cutting, Cr₂O₃ oxide appears on the wear surface while other elements are bound with N atoms. When the cutting length is increased to up to 260 m, oxide Al₂O₃ · ZrO₂ (mullite) and amorphous oxides TaO₂ and CrO₂ are formed. The method EELFS made it possible to determine the amorphous nanocrystalline structure of triboceramics based on CrO₂ and Al₂O₃ · ZrO₂. The nearest atomic surrounding of Cr-Cr, O-O, and Cr-O and their subsequent comparison with the available literature data allow us to calculate the equilibrium lattice constants of the CrO₂ unit cell, which are equal to (a, b) = 4.3754 Å and c = 0.5927. The triboceramic films on the base of non-equilibrium mullite Al₂O₃·ZrO₂ have an amorphous structure. In the first coordination sphere, the interatomic distances of Zr-O and Al-O were 1.79 and 1.89 Å. An accelerated adaptive reaction to extreme external stimuli, at the very beginning of the running-in stage, is established. The tribological adaptability of the high-entropy ultra-fine amorphous nanocrystalline coating under extremely loaded dry high-speed cutting is based on non-equilibrium phenomena: the partial oxidation of fragments of the nitride and dynamic formation of protective tribooxides, which have a good thermal barrier and frictional properties. These factors interact synergistically and determine the life of the cutting tool. Full article

Process capability analysis is the main tool of statistical process control. It is used for the ongoing monitoring of product compliance with imposed requirements. The main objective and novelty of the study were to determine the capability indices for a precision milling process of AZ91D magnesium alloy. Machining was performed in terms of variable technological parameters and using end mills with protective TiAlN and TiB₂ coatings intended for the machining of light metal alloys. The Pp and Ppk process capability indices were determined based on the measurements of the dimensional accuracy of the shaped components that were taken on a machining centre with a workpiece touch probe. Obtained results demonstrated that the type of tool coating and variable machining conditions had a significant impact on the machining effect. The selection of appropriate machining conditions enabled a terrific level of capability to be achieved at a tolerance of 12 µm, several times lower than under unfavourable conditions where the tolerance was up to 120 µm. Improvements in process capability are mainly achieved by adjusting the cutting speed and feed per tooth. It was also shown that process estimation based on improperly selected capability indices might lead to an overestimation of the actual process capability. Full article