Nanostructured Multilayer Composite Coatings for Cutting Tools

The chapter deals with the specific features concerning the application of wear-resistant coatings to improve the performance properties of ceramic cutting tools. The paper discusses the theoretical background associated with the specific operation conditions and wear of ceramic cutting tools and influencing the choice of the compositions and structures of wear-resistant coatings. The studies were focused on the application of the Ti-(Ti,Al)N-(Zr,Nb,Ti,Al)N multilayer composite coating with a nanostructured wear-resistant layer, as well as the (Cr,Al,Si)N–(DLC–Si)–DLC–(DLC–Si) and (Cr,Al,Si)N–DLC composite coatings in order to improve the cutting properties of ceramic tools. The chapter presents the results of the comparative cutting tests for the tools with the coatings under study, uncoated tools, and tools with the Ti-(Ti,Al)N commercial coating. The wear mechanisms typical for ceramic cutting tools with coatings of various compositions have been investigated

The Effect of Elemental Composition and Nanostructure of Multilayer Composite Coatings on Their Tribological Properties at Elevated Temperatures

The chapter discusses the tribological properties of samples with multilayer composite nanostructured Ti-TiN-(Ti,Cr,Al,Si)N, Zr-ZrN-(Nb,Zr,Cr,Al)N, and Zr-ZrN-(Zr,Al,Si)N coatings, as well as Ti-TiN-(Ti,Al,Cr)N, with different values of the nanolayer period λ. The relationship between tribological parameters, a temperature varying within a range of 20–1000°C, and λ was investigated. The studies have found that the adhesion component of the coefficient of friction (COF) varies nonlinearly with a pronounced extremum depending on temperature. The value of λ has a noticeable influence on the tribological properties of the coatings, and the nature of the mentioned influence depends on temperature. The tests found that for the coatings with all studied values of λ, an increase in temperature first caused an increase and then a decrease in COF

Investigation into Performance of Multilayer Composite Nano-Structured Cr-CrN-(Cr_0.35Ti_0.40Al_0.25)N Coating for Metal Cutting Tools

This paper deals with the Cr-CrN-(Cr0.35Ti0.40Al0.25)N coating. It has a three-layered architecture with a nano-structured wear-resistant layer. The studies involved the investigation into the microstructure (with the use of SEM and TEM), elemental and phase composition (XRD and SAED patterns), wear process pattern in scratch testing, crystal structure, as well as the microhardness of the coating. Cutting tests of tools with the above coating were carried out in dry turning of steel 1045 at cutting speeds of vc = 200, 250, and 300 m·min−1. The comparison included uncoated tools and tools with the commercial TiN and (Ti,Al)N coatings with the same thickness. The tool with the Cr-CrN-(Cr0.35Ti0.40Al0.25)N coating showed the longest tool life at all the cutting speeds under consideration. Meanwhile, a tool with the coating under study can be recommended for use in turning constructional steel at the cutting speed of vc = 250 m·min−1. At this cutting speed, a tool shows the combination of a rather long tool life and balanced wear process, without any threat of catastrophic wear

Specific Application Features of Ti-TiN-(Ti,Cr,Al)N, Zr-ZrN-(Zr,Mo,Al)N, and ZrHf-(Zr,Hf)N-(Zr,Hf,Cr,Mo,Al)N Multilayered Nanocomposite Coatings in End Milling of the Inconel 718 Nickel-Chromium Alloy

This article discusses the specific application features of end mills with Ti-TiN-(Ti,Cr,Al)N, Zr-ZrN-(Zr,Mo,Al)N, and ZrHf-(Zr,Hf)N-(Zr,Hf,Cr,Mo,Al)N multilayer nanocomposite coatings during the machining of the Inconel 718 nickel–chromium alloy. The hardness, fracture resistance during scratch testing, structure, and phase composition of the coatings were studied. The tribological properties of the samples were compared at temperatures of 400–900 °C. Tests were conducted to study the wear resistance of the coated end mills during the milling of the Inconel 718 alloy. The wear mechanism of the end mills was studied. It was found that in comparison with the other coatings, the Zr-ZrN-(Zr,Mo,Al)N coating had the highest hardness and the lowest value of the adhesion component of the coefficient of friction at high temperatures. However, the Zr-ZrN-(Zr,Mo,Al)N coating exhibited good resistance to cracking and oxidation during the milling of the Inconel 718 alloy. Based on the above, the Zr-ZrN-(Zr,Mo,Al)N coating can be considered a good choice as a wear-resistant coating for the end milling of the Inconel 718 alloy

Investigation of the Properties of Multilayer Nanostructured Coating Based on the (Ti,Y,Al)N System with High Content of Yttrium

The studies are focused on the properties of the multilayer composite coating based on the (Ti,Y,Al)N system with high content of yttrium (about 40 at.%) of yttrium (Y). The hardness and elastic modulus were defined, and the resistance to fracture was studied during the scratch testing. Two cubic solid solutions (fcc phases), including c-(Ti,Y,Al)N and c-(Y,Ti,Al)N, are formed in the coating. The investigation of the wear resistance of the (Ti,Y,Al)N-coated tools during the turning of steel in comparison with the wear resistance of the tools with the based on the (Ti,Cr,Al)N system coating and the uncoated tools found a noticeable increase (by 250%–270%) in rake wear resistance. Active oxidation processes are observed in the (Ti,Y,Al)N coating during wear. It can be assumed that yttrium oxide is predominantly formed with a possible insignificant formation of titanium and aluminum oxides. At the same time, complete oxidation of c-(Y,Ti,Al)N nanolayers is not observed. Some hypotheses explaining the rather high performance of a coating with a high yttrium content are considered

Investigation of the Influence of Microdroplets on the Coatings Nanolayer Structure

The paper presents the results of studies focused on the specific features typical for the formation of the shape and structure of microdroplets embedded into the structure of the Ti–TiN–(Ti,Cr,Mo,Al)N and Ti–TiN–(Ti,Al,Nb,Zr)N coatings during their deposition. Three main microdroplet shapes—a sphere, a tear, and a lens—have been considered. The specific features typical for the formation of secondary layered structures on the surface of some microdroplets have also been examined. As a result of the conducted investigations, with the use of scanning and transmission electron microscopy, the influence of microdroplets on the distortion of the nanolayer structure of the coatings was studied. A hypothesis has been proposed concerning a relationship between the microdroplet shape and the presence or absence of secondary structures and the microdroplet sizes and weight, as well as the conditions in the unit chamber during the movement of a microdroplet from a cathode to the deposition surface. Based on the study focused on the shape of the microdroplet core and the specific features typical for the formation of the secondary structure around it, a hypothesis has been proposed, according to which, for some microdroplets, it takes much more time than previously assumed for the movement from a cathode to the deposition surface

Investigation of the Properties of Multilayer Nanostructured Coating Based on the (Ti,Y,Al)N System with High Content of Yttrium

The studies are focused on the properties of the multilayer composite coating based on the (Ti,Y,Al)N system with high content of yttrium (about 40 at.%) of yttrium (Y). The hardness and elastic modulus were defined, and the resistance to fracture was studied during the scratch testing. Two cubic solid solutions (fcc phases), including c-(Ti,Y,Al)N and c-(Y,Ti,Al)N, are formed in the coating. The investigation of the wear resistance of the (Ti,Y,Al)N-coated tools during the turning of steel in comparison with the wear resistance of the tools with the based on the (Ti,Cr,Al)N system coating and the uncoated tools found a noticeable increase (by 250%–270%) in rake wear resistance. Active oxidation processes are observed in the (Ti,Y,Al)N coating during wear. It can be assumed that yttrium oxide is predominantly formed with a possible insignificant formation of titanium and aluminum oxides. At the same time, complete oxidation of c-(Y,Ti,Al)N nanolayers is not observed. Some hypotheses explaining the rather high performance of a coating with a high yttrium content are considered

Influence of Cutting Speed during the Turning of Inconel 718 on Oxidation Wear Pattern on the Zr-ZrN-(Zr,Mo,Al)N Composite Nanostructured Coating

The properties and oxidation wear patterns in the composite nanostructured coating of Zr-ZrN-(Zr,Mo,Al)N were studied during the turning of Inconel 718 alloy at the cutting speeds of vc = 125 and 200 m/min. The hardness of the coating, its elastic modulus, and critical fracture load during the scratch testing were determined. The study focused on the tribological properties of the Zr-ZrN-(Zr,Mo,Al)N coating at temperatures of 400–900 °C paired with an insert made of Inconel 718, which exhibited a certain advantage over the reference coatings of Zr-ZrN and Ti-TiN-(Ti,Cr,Al)N of similar thickness. The coating of Zr-ZrN-(Zr,Mo,Al)N provided for the longest tool life at the cutting speed of vc = 125 m/min (the tool life was four times longer in comparison with that of the uncoated tool and 15% longer in comparison with that of the Ti-TiN-(Ti,Cr,Al)N-coated tool) and at the cutting speed of vc = 200 m/min (the tool life was 2.5 times longer in comparison with that of the uncoated tool and 75% longer in comparison with that of the Ti-TiN-(Ti,Cr,Al)N-coated tool). While at the cutting speed of vc = 125 m/min, the surface coating layers exhibit only partial oxidation of the external layers (to a depth not exceeding 250 nm), with mostly preserved cubic nitride phases, and then the cutting speed of vc = 200 m/min leads to almost complete oxidation (to the depth of at least 500 nm), however, with a partially preserved nanolayered structure of the coating

Influence of niobium and hafnium doping on the wear and corrosion resistance of coatings based on ZrN

The properties of coatings based on the ZrN system with the introduction of hafnium and zirconium (ZrN, (Zr,Nb)N and (Zr,Hf)N), deposited on a Ti6Al–4V titanium alloy substrate are compared. Coatings are deposited by controlled accelerated arc-physical vapor deposition, and the structure of the coatings is studied using a transmission electron microscope. A comparison is made of both the mechanical (hardness, wear resistance, scratch strength) and anticorrosion (in a 3 % solution of NaCl) properties. The (Zr,Hf)N coating (22 at% Hf and 78 at% Zr) has the maximum hardness (HV, 3225 ± 73) and wear resistance. This coating also exhibits higher corrosion resistance. In contrast, introducing Nb into the coating composition reduces the corrosion resistance. This combination of beneficial properties makes the (Zr,Hf)N coating useful for conditions in which the surfaces of parts must simultaneously have high wear resistance, strength, and corrosion resistance

Influence of the Ti-TiN-(Y,Ti,Al)N Nanolayer Coating Deposition Process Parameters on Cutting Tool Oxidative Wear during Steel Turning

Ti-TiN-(Y,Ti,Al)N coatings with a three-layer architecture (adhesive Ti layer, transition TiN layer, and wear-resistant (Y,Ti,Al)N layer) were studied. When depositing coatings, three arc current values of the yttrium cathode were used: 65, 85, and 105 A. The yttrium contents in the coatings were 30, 47, and 63 at. %, respectively. When turning 1045 steel, a coating with 30 at. % yttrium showed better wear resistance compared to a commercial (Ti,Cr,Al)N coating. The coating with 63 at. % yttrium did not show an increase in wear resistance compared to the uncoated sample. Nanolayers with a high yttrium content are oxidized more actively compared to nanolayers with a high titanium content. Phase analysis shows partial retention of the initial phases (Y,Ti,Al)N and (Ti,Y,Al)N during the formation of the Y2O3 oxide phase in the outer layers of the coating and the presence of only the initial phases in the deep layers. Coating nanolayers with high contents of aluminum and yttrium lose their original structure to a greater extent during oxidation compared to layers without aluminum