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Ti(C,N)-based cermets with a CoCrFeMnNi high-entropy alloy (HEA) binder phase were coated via chemical vapor deposition (CVD). The influence of the HEA-bonded cermet substrate on the microstructure, orientation, adhesion, and high temperature frictional wear performance of the CVD coating was investigated. The results indicate that the HEA binder phase inhibits the growth of cermet grains and provides more nucleation sites for the coating. Thus, the coating on the HEA-bonded cermet has a smaller grain size. The substitution of HEA for the Ni binder phase increases the entropy value of the cermet system, resulting in a decrease in free energy. In the early stage of CVD, the gas atoms adsorbed on the solid surface with low free energy are in a more stable thermodynamic state, which enhances the adhesion strength between the coating and substrate. During high temperature frictional wear, the friction coefficient of the coating on Ni-bonded cermet is less than that of the coating on HEA-bonded cermet because of iron oxide lubricating films. However, the wear rate exhibits a reverse trend. The coating on the HEA-bonded cermet has the best wear resistance due to small grain size, superior hardness and excellent adhesion strength. The wear forms present in the CVD coatings are abrasive wear, adhesive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

The tribological behavior of tenfold micro/nanocrystalline CVD diamond multilayers is here investigated in self–mated configuration using ball-on-plate reciprocating wear testing. The effects of relative humidity (RH) and temperature (T) on friction and wear coefficients are assessed. The strongest effect of humidity was found on the value of the critical load (no delamination) that triples from 40 N at 10%RH to 120 N at 90%RH. Evaluation of the wear coefficients of the plates was only possible with the use of 3D optical profilometry. A valley-shaped evolution is observed for the wear coefficient of the plates, within the 10% to 90% RH range, with a minimum of about 1.7x10 -7 mm 3 N -1 .m -1 , indicative of a mild wear regime, whereas the balls have lower values in the very mild wear regime of k ~ 10 -8 mm 3 N -1 .m -1 . The clearest difference between the RH and temperature experiments is observed for the critical loads, limited to the range 40-55 N at 50-100°C, while at room temperature a value of 120 N was reached. However, the critical loads at high temperature are similar to those attained under dry conditions (≤ 25% RH) highlighting the absence of water as the load bearing medium. [ABSTRACT FROM AUTHOR]

Material transfer from the work materials to the tools strongly influences machining performance and tool life. The influence of Si and Al additions to carbon steel on the material transfer and coating wear in turning with CVD coated carbide tools is investigated. Three model steels are specifically designed to separately study the effects of the individual alloying elements: one reference steel with C as the only alloying element (Base steel), and two steels alloyed also with 1 mass% Si or Al. In the region around the depth of cut on the rake face, where the outside edge of the chip passes over the tool surface, the coating is worn mainly by abrasion when cutting the Base steel. When cutting the Si alloyed steel, an almost pure Si–O transfer layer covers the coating surface, which protects it from wear. When cutting the Al alloyed steel, an almost pure Al–O transfer layer forms on the coating. This layer promotes steel transfer and associated adhesive wear of the coating, which rapidly results in coating detachment and eventually causes notch wear. In the crater region, only the Al alloyed steel results in a transfer layer, an AlN layer that reduces the crater wear. [ABSTRACT FROM AUTHOR]

Mechanism of silicon carbide coating on the internal surface of the graphite tube of dimension ϕ 3 mm ID × ϕ 10 mm OD × ϕ 235 mm and surface area ∼24.5 cm 2 has been investigated. Atmospheric pressure chemical vapor deposition (APCVD) method in mass controlled domain has been applied. Methyltrichlorosilane (MTS) as precursor was used in the present investigation. The coating was characterized by X-ray micro tomography (μCT). The coating thickness and composition were analyzed by scanning electron microscopy energy-dispersive spectroscopy (SEM–EDS). The coating phase analyzed by X-ray diffraction (XRD). It has been concluded that silicon carbide coating is a predominantly boundary layer phenomena and the engineering of the same could open up the prospects to accomplish SiC coating on complex pipe line structures on macro scale. [ABSTRACT FROM AUTHOR]

Abstract: Multilayer thin film systems on polymeric substrates are investigated as abrasion resistant reflective coatings for the development of light weight optical devices. In this investigation, the influence of the coating''s material properties on its abrasion resistance is determined with a step increase in abrasion resistance demonstrated upon application of an ultrathin capping layer, ca. 5–15nm. These ultrathin capping layers reduce the surface roughness and coefficient of friction of the coating system, resulting in a greater resistance to wear. Despite the soft nature of the underlying polymeric substrate, the engineered coating system allows such devices to outperform their conventional glass-based counterparts in the design of light weight products for a range of optical applications. [Copyright &y& Elsevier]

The first results of different new sheet-bulk forming methods are presented in the article. It is shown how an additional superimposing of oscillation can be attached to the forming punch in order to improve the forming limit of the sheet material. New coating and atmospheric plasma-nitriding methods for processing of the forming tools (for improving of hardness and wear resistance) are also represented in the article. [ABSTRACT FROM AUTHOR]

Abstract: Conditioning of polishing pads during chemical mechanical planarization (CMP) of wafers is a critical process for maintaining productivity and quality control in the semiconductor industry. This investigation aims at developing a CMP diamond conditioner of a new concept and hence improving the conditioning performance. The novel diamond conditioner was fabricated by coating diamond films on a Si3N4 substrate with regularly patterned protrusions. Thanks to the uniform distribution and constant height of protrusions, the novel conditioner exhibited superior performance and durability over the current conditioner, which contains bonded diamond grits of various sizes and shapes with unequal heights. Characterization of the developed novel diamond CVD conditioner has also been made. [Copyright &y& Elsevier]

Abstract: The reliability and performance of silicon carbide (SiC) shaft seals on multipurpose mechanical pumps are improved by applying a protective coating of ultrananocrystalline diamond (UNCD). UNCD exhibits extreme hardness (97GPa), low friction (0.1 in air) and outstanding chemical resistance. Consequently, the application of UNCD coatings to multipurpose mechanical pump seals can reduce frictional energy losses and eliminate the downtime and hazardous emissions from seal failure and leakage. In this study, UNCD films were prepared by microwave plasma chemical vapor deposition utilizing an argon/methane gas mixture. Prior to coating, the SiC seals were subjected to mechanical polishing using different grades of micron-sized diamond powder to produce different starting surfaces with well-controlled surface roughnesses. Following this roughening process, the seals were seeded by mechanical abrasion with diamond nanopowder, and subsequently coated with UNCD. The coated seals were subjected to dynamic wear testing performed at 3600RPM and 100psi for up to 10 days during which the seals were periodically removed and inspected. The UNCD-coated seals were examined using Raman microanalysis, scanning electron microscopy, optical profilometry, and adhesion testing before and after the wear testing. These analyses revealed that delamination of the UNCD films was prevented when the initial SiC seal surface had an initial roughness >0.1μm. In addition, the UNCD surfaces showed no measurable wear as compared to approximately 0.2μm of wear for the untreated SiC surfaces. [ABSTRACT FROM AUTHOR]

Abstract: Coated cemented carbide is a key material for cutting tools and its manufacturing includes pretreatment of the substrate surface before coating deposition. To obtain a durable tool edge, this pretreatment must achieve two objectives: high adhesive strength of the substrate-coating interface and low coating surface roughness to reduce friction with the workpiece and the chips removed during the machining process. Several methods have been researched for substrate surface pretreatment, including micro-sandblasting—the standard industrial procedure, which is an economic and effective process. In this work, a laser substrate surface treatment was examined as an alternative to micro-sandblasting, because the laser process does not produce waste material flux, allows for the selective treatment of surface areas, and involves a potentially shorter processing time per piece. A pulsed CuHBr laser (510nm, 30ns, 13.8kHz) was used, and for the tested MT-CVD TiCN/Al2O3/TiN coated cemented carbide cutting tools, the optimal laser intensity and number of laser shots were identified by trial-and-error based on the Rockwell C adhesion test. Using the optimal set of laser parameters, a group of tools was then prepared for face end milling tests on P20 mold steel. Lastly, a comparison was made of the tool lifetime, tool wear profile, and tool wear mechanisms of the experimental laser-treated tools and the commercial micro-sandblasted ones. [Copyright &y& Elsevier]

Abstract: The increasing demand for quality on moulded polymer parts is stressing the research and development on new and enhanced injection moulding materials and tools. The latter, is the objective of the study reported here focusing the research on moulds with considerable lower adhesion walls and simultaneously better mould heat extraction rates. Polycrystalline diamond coatings enable the attainment of both characteristics above highlighted, inferring to the mould wall a higher thermal conductivity coefficient and one of the lowest friction coefficients. Recent developments in the diamond chemical vapour deposition (CVD) process, combined with the usage of appropriated interlayer systems, open the possibility to apply polycrystalline diamond coatings onto steel mould inserts. Therefore, this study reports results obtained on the properties of diamond thin films deposited on typical mould steel, and preliminary results on the interaction between the diamond/steel system and the melt polymer. [Copyright &y& Elsevier]

The high temperature oxidation behaviors of chromia-forming alloys (F17Ti and Fe–30Cr alloys) have been studied at 1273 K under isothermal conditions and at 1223 K under cyclic conditions, in air under the atmospheric pressure. To extend the oxidation lifetime, coatings have been applied onto the alloy surfaces. Al2O3 and Cr2O3 films doped with Sm2O3 or Nd2O3 were prepared via the metal-organic chemical vapor deposition technique. Single Cr2O3, Al2O3, Nd2O3 and codeposited Cr2O3–Nd2O3, Al2O3–Nd2O3, Al2O3–Sm2O3 coatings drastically improved the chromia-forming alloy high temperature oxidation behavior, since they decreased the oxidation rate and enhanced the oxide scale adhesion. Results showed that a critical amount of reactive element (Nd or Sm) in chromia or alumina coatings (11–18 at.%) was needed to observe the most effective effect. The fast precipitation of NdCrO3 or NdTi21O38 and the segregation of reactive elements at the chromia grain boundaries slowing down outward cation transport and consequently blocking the chromia grain growth, was supposed to be the main reasons of the beneficial effect ascribed to the reactive elements in chromia scales. [Copyright &y& Elsevier]

Transition metal nitride based hard coatings are widely applied in metal cutting, however, there are still drawbacks in metal forming processes limiting their implementation. The aim of this study is thus to discuss deposition processes suitable for coating of the often large and three-dimensional molds and dies used in metal forming. Furthermore, results obtained using different hard coatings in industrial applications for several case studies like aluminum pressure die-casting, plastics injection molding and sheet metal forming are presented and discussed. For best coating performance, a careful optimization of both substrate pre-treatment and coating deposition is necessary. The plasma-assisted chemical vapor deposition (PACVD) technique shows advantages for these applications because of the high flexibility in pre-treatment using chemical etching and plasma-nitriding, because of its ability to coat large complexly shaped tools and because of the possibility of deposition of low-chlorine containing low-friction coatings. Typical factors for the increase in lifetime in aluminum pressure die-casting are between 2 and 4, in plastics injection molding more than 10 and in deep drawing of 13 with respect to uncoated tools. [Copyright &y& Elsevier]

The ability to control the shape, distribution and composition of non-metallic inclusions has had an important impact on many aspects of steel making. One such impact is on the machinability. Ca-treatments have shown to be able to reduce the abrasiveness of oxide inclusions, improve chip-breaking and lead to formation of deposits that reduce tool wear. However, machining Ca-treated steels with Al 2 O 3 coated cemented carbide tools has not been as advantageous as expected. This study investigates the mechanisms behind the anomalous wear of Al 2 O 3 coatings when turning soft Ca-treated steels. Longitudinal turning tests at a range of speeds (v c = 100–600 m/min) show rapid localized degradation of the Al 2 O 3 coating limited to the sliding zone. Detailed analysis of the degradation mechanisms was performed using scanning and transmission electron microscopy. The results demonstrate a presence of chemical interactions between the alumina coating and non-metallic inclusions. The interaction resulted in the formation of mainly calcium aluminates and partly alumina-magnesia spinel. In-operando infrared thermography measurements indicate cutting temperatures of 850–1000 °C. Thermodynamic calculations give that CaO and MgO readily reacts with Al 2 O 3 , while the reaction with CaS requires presence of additional oxygen at these cutting conditions. Additional turning experiments investigate the influence of oxygen by controlling the cutting environment by adding oxygen (compressed air) or removing oxygen (supply argon). These additional tests show that the presence of additional oxygen has a limited impact on the possible Ca–Al 2 O 3 interaction. This demonstrat a potential for further machinability improvements by controlling the chemical interaction between Ca and Mg based non-metallic inclusions and alumina coatings. • The inertness of alumina coatings has previously been overestimated. • Ca and Mg based non-metallic inclusions can degrade Al 2 O 3 coatings. • (Ca,Mg,Al) x O y form between the coating and chip. • Atmospheric oxygen does not increase the rate of degradation. • Creating a possibility for further development of Ca-treatments. [ABSTRACT FROM AUTHOR]

The evolution of damage induced as contact load is increased has been investigated on single- and multilayered coated cemented carbides by means of spherical indentation. The main objective of the study was to assess the effect of the intermediate wear-resistant carbonitride layer on the contact damage resistance of industrial milling (multilayered) inserts. This was approached by evaluating systems consisting of a single carbonitride layer of different chemical nature: novel Zr(C,N) and conventional Ti(C,N) chemical vapor deposition (CVD) coatings. Deformation and damage phenomena were characterized using a wide range of advanced techniques: confocal laser scanning microscopy, scanning electron microscopy, focused ion beam and X-ray synchrotron. Zr(C,N) coated systems are found to exhibit a higher mechanical integrity than Ti(C,N) counterparts. Main reasons behind are the relatively different thermal residual stresses generated during CVD cooling, as a result of the dissimilar coefficient of thermal expansion between the coating and the substrate, as well as the intrinsic cohesive strength of the studied coatings. Such different mechanical response was also discerned to affect the interaction between cracking and layer assemblage in multilayer coated specimens. It then supports the beneficial effect of using Zr(C,N) as the intermediate wear-resistant layer toward enhanced performance of industrial milling inserts. • Zr(C,N) coated systems exhibit higher mechanical integrity than Ti(C,N) ones. • Contact damage depends on surface integrity and residual stresses of layers. • Crack propagation path is intergranular for Ti(C,N) and mainly transgranular for Zr(C,N). • Crack propagation path results agree with previous micro-compression experiments. [ABSTRACT FROM AUTHOR]