Filtered cathodic vacuum Arc deposition of nano-layered composite coatings for machining hard-to-cut materials

In coated tools, the grain boundaries and coating layers are areas of intense energy dissipation, which hardens the coating material by increasing its toughness and its resistance to the formation and development of cracks. An increase in the efficiency of the coatings was achieved by applying nano-dispersed multilayer composite structure. This paper proposes using nano-scale multilayer composite coating based on TiN-CrN compound to improve thermal stability, where barrier layers based on ZrNbN have been introduced. The ZrNbN barrier does not interact with TiN and CrN at temperatures around 1000 °C. The influence of process parameters of the filtered cathodic vacuum arc deposition on the composition, structure and properties of the coatings based on variation of TiAlN-ZrNbN-CrN was analysed. The results presented here show that the hardness of the developed coatings was as high as 38 GPa. Subsequently, the carbide tools used in this study with the new coatings had an increased lifetime of 1.5–2.0 times compared to tools with commercial coatings. The coated carbide tools were tested in longitudinal turning and face milling titanium and nickel alloys

Application of carbide cutting tools with nano-structured multilayer composite coatings for turning austenitic steels, type 16Cr-10NI

This paper addresses the challenges of increasing the efficiency of the machining of austenitic stainless steels AISI 321 and S31600 by application of cutting tools with multilayer composite nano-structured coatings. The main mechanical properties and internal structures of the coatings under study (hardness, adhesion strength in the "coating-substrate" system) were investigated, and their chemical compositions were analyzed. The conducted research of tool life and nature of wear of carbide tools with the investigated coatings during turning of the above mentioned steels showed that the application of those coatings increases the tool life by up to 2.5 times. In addition, the use of a cutting tool with coatings allows machining at higher cutting speeds. It was also found that the use of a tool with multilayer composite nano-structured coating (Zr,Nb)N-(Zr,Al,Nb)N ensures better results compared with not only monolithic coating TiN, but also with nano-structured coatings Ti-TiN-(Ti,Al)N and (Zr,Nb)N-(Cr,Zr,Nb,Al)N. The mechanism of failure of the coatings under study was also investigated. © 2017 AFM, EDP Sciences

УПРОЧНЕНИЕ ТВЕРДОСПЛАВНОГО ЛЕЗВИЙНОГО ИНСТРУМЕНТА, ИСПОЛЬЗУЕМОГО ДЛЯ РЕЗАНИЯ ТРУДНООБРАБАТЫВАЕМЫХ ТИТАНОВЫХ СПЛАВОВ И ХРОМОНИКЕЛЕВЫХ СТАЛЕЙ, МНОГОСЛОЙНЫМИ НАНОСТРУКТУРНЫМИ ПОКРЫТИЯМИ

Complex investigations into physicomechanical properties and adhesion strength in the «coating–carbide cutting insert» system of monolayered (Ti–Al–N) and multilayered (Ti–Al–N/Cr–N, Ti–Al–N/Zr–N/Cr–N) are performed. The advantage of using the latter; which is associated with the passage from the adhesion mechanism of coating destruction to the cohesion mechanism; with an increase in parameters H3/E2 and H/E that characterize the material resistance to plastic and elastic deformation, respectively; is shown. The introduction of chromium into the composition of Ti–Al–N coatings provides a decrease in friction coefficient (from 0,52 to 0,45) and a decrease in probability of adhesion interaction with the treated material. Comparative operational tests of carbide cutting insets (CCI) with coatings under study in the course of continuous cutting steel 12H18N10Т showed that largest wear resistance of Ti–Al–N/Zr–N/Cr–N coatings. Wear tests of CCIs made of VK6NST and TT10K8B alloys with Ti–Al–N/Zr–N/Cr–N coatings in the course of longitudinal turning steel 12H18N10Т and VT20 alloy evidence an increase in their resistance up to a factor of 3,0–3,5 both at low and high cutting rates. These coatings provide an increase in resistance of cutting tool and in milling operations of VT20 titanium alloy at cutting velocity up to 40 m/min.Проведены комплексные исследования физико-механических свойств и адгезионной прочности в системе «покрытие – твердосплавная подложка» монослойных (Ti–Al–N) и многослойных (Ti–Al–N/Cr–N, Ti–Al–N/Zr–N/Cr–N) покрытий. Показано преимущество использования последних, которое связано с переходом от механизма адгезионного разрушения покрытия к когезионному, с повышением параметров H3/E2 и H/E, характеризующих сопротивление материала пластической и упругой деформации соответственно. Введение в состав покрытий Ti–Al–N хрома обеспечивает снижение коэффициента трения (c 0,52 до 0,45) и уменьшение вероятности адгезионного взаимодействия с обрабатываемым материалом. Сравнительные эксплуатационные испытания твердосплавных сменных многогранных пластин (СМП) с исследуемыми покрытиями при непрерывном резании стали 12X18H10Т показали наибольшую износостойкость покрытий Ti–Al–N/Zr–N/Cr–N. Стойкостные испытания СМП из сплавов ВК6НСТ и ТТ10К8Б с покрытиями Ti–Al–N/Zr–N/Cr–N при продольном точении стали 12Х18Н10Т и сплава ВТ20 свидетельствуют об увеличении их стойкости до 3,0–3,5 раз как при низких, так и высоких скоростях резания. Данные покрытия обеспечивают повышение стойкости режущего инструмента и на операциях фрезерования титанового сплава ВТ20 при скорости резания до 40 м/мин

Effect produced by thickness of nanolayers of multilayer composite wear-resistant coating on tool life of metal-cutting tool in turning of steel AISI 321

The paper considers multilayer composite nano-structured Ti-TiN-(Ti,Al,Cr,Si)N coatings for metal-cutting tools. The coatings under the study mechanical characteristics of the coatings were studied, and the tool life tests were carried out for carbide tools with the above coatings for dry about 80 nm). The turning of steel AISI 321(HB 180) at vc = 100, 150, and 200 m/min (f=0.11 mm/rev; ap=0.5 mm). Uncoated tools and tools with Ti-(Ti,Al)N coatings of traditional type were used as objects of comparison. The studies have found out that coatings with thinner nanolayers demonstrate better performance properties, especially at higher cutting speeds. © 2018 The Authors. Published by Elsevier Ltd

ТВЕРДОСТЬ, АДГЕЗИОННАЯ ПРОЧНОСТЬ И ТРИБОЛОГИЧЕСКИЕ СВОЙСТВА АДАПТИВНЫХ НАНОСТРУКТУРНЫХ ИОННО-ПЛАЗМЕННЫХ ВАКУУМНО-ДУГОВЫХ ПОКРЫТИЙ (Ti,Al)N–Mo2N

The article reviews the properties of nanostructured multilayer coatings (Ti, Al)N–Mo2N obtained by plasma-ion vacuum arc deposition method (arc-PVD). The thickness of coating layers was comparable to the size of a grain, which was about 30–50 nm. Coating hardness reached 40 GPa with relative plastic work of deformation of about 60 %. It was found by the measuring scratching method that cohesive nature of coating destruction takes place entirely by a plastic strain mechanism, which was the evidence of its high viscosity. Local coating abrasion to a substrate level occurred at a load in the order of 75 N. Under test conditions as per «pin-on-disk» scheme using the opposing Al2O3 element at a load of 5 N, coating friction factor was equal to 0,35 and 0,50 at 20 °C and 500 °C respectively. Besides, it was practically not worn due to formation of MoO3 oxide in the friction zone (Magneli phase) which served as a solid lubricant. The increase in friction factor and appearance of significant wear were observed with further rising of test temperature. Such effect was due to intensified sublimation of MoO3 from friction surfaces with subsequent reduction of its lubricating efficiency.Исследованы свойства наноструктурных мультислойных покрытий состава (Ti,Al)N–Mo2N, полученных методом ионно-плазменного вакуумно-дугового осаждения (arc-PVD). Толщина слоев покрытия сопоставима с размером зерна, который составлял порядка 30–50 нм. Твердость покрытий достигала 40 ГПа с относительной работой пластической деформации около 60 %. Методом измерительного царапания установлено, что когезионный характер разрушения покрытия происходит исключительно по механизму пластического деформирования, что свидетельствует о высокой его вязкости. Локальное истирание покрытия до подложки происходило при нагрузке порядка 75 Н. Коэффициент трения покрытия в условиях испытаний по схеме «стержень–диск» с применением контртела из Al2O3 при нагрузке 5 Н составлял 0,35 и 0,50 при температурах 20 и 500 °C соответственно. При этом оно практически не изнашивалось из-за образования в зоне трения оксида MoO3 (фазы Магнели), работающего в качестве твердого смазывающего материала. При дальнейшем повышении температуры испытания наблюдалось повышение коэффициента трения и появление заметного износа, что связано с интенсификацией процессов сублимации MoO3 с рабочих поверхностей и снижением эффективности его работы как смазывающего материала