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Item type:Publication, Access status: with files , Oxidation and wear behavior of CrAlMoN with varied Mo-content for cutting Ti6Al4V(Springer, 2023-08-03); ; ; ; The cutting of difficult to machine materials such as titanium alloys is challenging for the machining industry. In case of the titanium alloy Ti6Al4V, the properties of the material cause high temperatures, mechanical loads as well as high frequency vibrations at the cutting edge, leading to premature tool failure. The use of uncoated carbide tools is very common for machining of Ti based alloys. However, temperature active, self-lubricating physical vapor deposition (PVD) coatings like CrAlMoN showed promising results to reduce friction and wear during turning of Ti6Al4V. In the present study, self-lubricating (Cr34Al41Mo25)N, (Cr29Al36Mo35)N and (Cr25Al31Mo44)N coatings were investigated on cemented carbide tools. These were deposited by a hybrid process combining direct current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering. Coating morphology, thickness, chemical composition, indentation hardness and modulus at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C as well as the oxidation behavior were analyzed. Moreover, wear development after cutting tests using a CNC-lathe was investigated. Independent of Mo-content, all coating variants possessed a dense morphology and a smooth surface topography, as well as a coating adhesion class of HF1 to the cemented carbide substrate in Rockwell indentation tests according to DIN 4856. With an increasing amount of Mo, heat treatment temperature and time, more self-lubricating molybdenum oxides such as MoO3 and Mo4O11 were detected by Raman spectroscopy. Therefore, the coating with the highest amount of Mo possessed the highest amount of molybdenum oxides. After cutting tests, molybdenum oxides were also found on the tool flank face by Raman spectroscopy. The level of flank wear land width decreased with increasing amount of Mo.Publicationtype: Journal Article50 11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Self-lubricating CrAlMoN high performance tool coatings for machining of TiAl6V4TiAl6V4 allows significant performance improvements in industrial applications. However, the machining is a considerable challenge due to low thermal conductivity, Young’s modulus and strong adhesion tendency. This leads to high thermal and mechanical loads on the cutting edge resulting in early tool failure. Today, uncoated cemented carbide tools are commonly used. However, temperature active physical vapor deposition (PVD) coatings like CrAlVN and CrAlMoN provide a promising approach to increase tool life. For this, the coating’s ability to form lubricating oxide phases is vital. In the present study, CrAlVN and CrAlMoN coatings were investigated to determine the more suitable version for increasing the economic efficiency of machining TiAl6V4. The coatings were deposited by hybrid direct current magnetron sputtering/high power pulsed magnetron sputtering (dcMS/HPPMS) processes. Morphology, thickness, chemical composition, indentation hardness, indentation modulus and oxide phase composition were analyzed. Moreover, friction and wear behavior of the coated tools were determined using a pin on disc (PoD) tribometer at various temperatures. Additionally, tool life and deformation behavior were analyzed after turning TiAl6V4. The CrAlVN and CrAlMoN coatings show a dense morphology and a smooth surface topography. Both variants have a good adhesion to the cemented carbide tools. For increased temperatures, the tribological analyses showed a reduction in the coefficient of friction. In case of CrAlMoN coated samples, a friction reduction compared to CrAlVN was observed at lower temperatures. Due to this, an increased tool life was achieved for CrAlMoN coated cutting inserts during turning of TiAl6V4.Publicationtype: Journal ArticleScopus© Citations 1 79 74 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 53 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Self-lubricating CrAlVN coatings for turning of Ti6Al4V: oxidation and wear behavior(Wiley-VCH, 2021-12-15); ; ; ; The titanium alloy Ti6Al4V enables significant performance increases in various branches of industry. Nevertheless, it is difficult to machine, because of its material properties. Due to the low thermal conductivity of titanium, the heat generated while turning Ti6Al4V mainly flows into the tool leading to high temperature loads. In addition, the comparatively low Young’s modulus and high yield strength contributes to high mechanical stresses during machining. Temperatureactive, self-lubricating physical vapor deposition hard coatings appear to be suitable for reducing friction and tool wear during turning of Ti6Al4V compared to the most commonly used uncoated carbide tools. The ability of the coating to form lubricating oxide phases at high temperatures is crucial for this purpose. This paper investigates the oxidation and diffusion behavior of vanadium doped chromiumaluminium nitride (CrAlN) coatings after heat treatment at ϑ=600°C, ϑ=700°C and ϑ=800°C in atmosphere as well as the resulting coating properties. The wear behavior of certain coating variants while turning of Ti6Al4V is analyzed.Publicationtype: Journal ArticleScopus© Citations 1 94 194 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Wear development of self-lubricating CrAlVN coatings during turning Ti6Al4V(Social Science Electronic Publ., 2021-12); ; ; ; Interactions between cutting tool and workpiece material are crucial to tool wear at the cutting edge. In particular difficult to machine materials like the titanium alloy Ti6Al4V require tailored solutions to avoid extensive tool wear. Temperature-active, self- lubricating chromium-aluminium-vanadium-nitride (CrAlVN) coatings deposited by physical vapor deposition (PVD) have shown the potential to reduce tool wear during Ti6Al4V turning. These coatings form lubricating oxide phases at temperatures between 700 °C ≤ θ ≤ 800 °C which might be suitable to reduce thermal and mechanical loads during cutting. However, the initial wear development as well as the formation of lubricating oxide phases during Ti6Al4V turning while using cooling lubricant have not been adequately investigated. Consequentially, it is unclear whether the lubricating oxide phases form during the turning operation with flood cooling. Nevertheless, this is of interest, because the use of cooling lubricant is state of the art in turning of Ti6Al4V in order to reach an increased tool life. That is why, the initial tool wear within the first two minutes of turning with flood cooling was investigated in this study. For this purpose, two different CrAlVN coatings with varying V/Al ratios were deposited on cemented carbide inserts by a hybrid direct current magnetron sputtering (dcMS) / high power pulsed magnetron sputtering (HPPMS) process using an industrial coating unit. Subsequently, cutting tests with a depth of cut ap = 1.2 mm, feed rate f = 0.12 mm, setting angle κr = 95° and cutting velocity vc = 80 m/min were conducted at defined cutting intervals of tc = 5 s, 10 s, 20 s, 40 s, 80 s and 120 s using a computer numerical controlled (CNC) lathe machine. The initial tool wear development, prevailing wear mechanisms as well as the formed oxide phases during the intervals were analyzed. Uncoated cemented carbide inserts were used as a reference. The results highlight that the formation of lubricating vanadium oxides is possible in turning process with cooling lubricant. Furthermore, it seems that adhesion processes are the main causes of tool failure. The results offer the possibility to adapt the CrAlVN coatings for Ti6Al4V turning.Publicationtype: Journal Article105 220