Hard Metal Layer Research Articles

Mathematical Modeling of Roughness Changing of Hard Metal Coatings Obtained by Contactless Electrospark Deposition

Results of the roughness studies of multicomponent hard metal layers on X12 tool steel (210Cr12/1.8–2.2% C, 12%Cr) obtained by contactless local electrospark deposition using two types hard metal electrodes (WC–TaC–Co–Al2O3 and WC–(Ti, Ta, Nb)C–Co–Al2O3) are presented here. Dense, smooth, and uniform coatings with a good repeatability of properties have been obtained. The minimal and maximal values of thickness δ, of the roughness parameter Ra, and of micro hardness HV of obtained coatings are changed by altering the stratification regimes in borders: δ = 3–12 μm, Ra = 0.8–2.2 μm and HV = 8.5–18 GPa, respectively. The influence of the process parameters and the electrode composition on the roughness of the layers obtained have been studied. Mathematical-statistical models and equations describing the roughness of the coatings have been created and worked out. They enable obtaining of coatings with a predetermined roughness by controlling regime parameters. Specific ways of obtaining coatings with reduced roughness at the maximum possible thickness, as well as recommendations for their appropriate application, have also been proposed and justified. Based on the obtained regression equations and graphical dependencies, it is possible to optimize properties of the coatings and the conditions of their deposition in order to obtain maximum tribo-effect and increased performance properties of the coated surfaces for different cases of exploitation.

Selection of di(meth)acrylate monomers for low pollution of fluorinated mold surfaces in ultraviolet nanoimprint lithography.

We used fluorescence microscopy to show that low adsorption of resin components by a mold surface was necessary for continuous ultraviolet (UV) nanoimprinting, as well as generation of a low release energy on detachment of a cured resin from a template mold. This is because with low mold pollution, fracture on demolding occurred at the interface between the mold and cured resin surfaces rather than at the outermost part of the cured resin. To achieve low mold pollution, we investigated the radical photopolymerization behaviors of fluorescent UV-curable resins and the mechanical properties (fracture toughness, surface hardness, and release energy) of the cured resin films for six types of di(meth)acrylate-based monomers with similar chemical structures, in which polar hydroxy and aromatic bulky bisphenol moieties and methacryloyl or acryloyl reactive groups were present or absent. As a result, we selected bisphenol A glycerolate dimethacrylate (BPAGDM), which contains hydroxy, bisphenol, and methacryloyl moieties, which give good mechanical properties, monomer bulkiness, and mild reactivity, respectively, as a suitable base monomer for UV nanoimprinting under an easily condensable alternative chlorofluorocarbon (HFC-245fa) atmosphere. The fluorescent UV-curable BPAGDM resin was used for UV nanoimprinting and lithographic reactive ion etching of a silicon surface with 32 nm line-and-space patterns without a hard metal layer.

A New Solution for the Compression of a Two-Layer Strip and Its Application to Analysis of Bonding by Rolling

The paper presents a theoretical study on the compression of a two-layer strip of strain-hardening rigid-plastic materials between rigid platens. Semianalytical solutions are obtained for stress and velocity fields in each layer. Special attention is devoted to the conditions corresponding to the beginning of cold bond formation between the layers. Depending on input parameters various general deformation patterns are possible. In particular, there exists such a range of process parameters that the soft metal layer yields while the hard metal layer is rigid at the beginning of the process. As the deformation proceeds, yielding also starts in the hard metal layer and the entire strip becomes plastic. This is a typical deformation pattern adopted in describing the process of joining by rolling. However, at a certain range of input parameters plastic deformation of the entire strip begins at the initial instant. Moreover, it is possible that only the hard metal layer yields while the soft metal layer does not. This deformation pattern takes place when the thickness of the soft metal layer is much smaller than that of the hard metal layer.

Decomposition Mechanism and Decomposition Promoting Factors of Waste Hard Metal for Zinc Decomposition Process (ZDP)

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc steam pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 hrs at 650 °C, which 100 % decomposed the waste hard metals that were over 30 mm thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of γ-β1 phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at 1000 °C. The small amount of zinc remaining in the tungsten carbide-cobalt powder which was completely decomposed was fully removed by using phosphate solution which had a slow cobalt dissolution speed.

Droplet erosion performance of composite materials electroplated with a hard metal layer

Abstract The effectiveness of resistance to water droplet erosion of various electro-deposited metal layers on glass fibre reinforced polymer (GFRP) was investigated. The number of impacts by 2 mm droplets at 225 m s −1 that could be applied before visible damage to the GFRP occurred was significantly higher with the metallic coatings than without. The impact resistance was found to increase in the order: Cu-only

ZDP(Zinc Decomposition Process)를 이용한 폐 초경합금의 분해기구

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc valatilization pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 h at 650℃, which 100 % decomposed the waste hard metals that were over 30 ㎜ thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of γ-β₁ phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at 1000℃.

Kinetics of Electroreduction of Cr3+Ions in Sulfate Solutions

Kinetics of electroreduction of Cr3+ions in an electrolyte based on Cr3+sulfate, which permits to produce thick (up to 100 μm) hard metal layers, is studied. The chemical stage of rearrangement of Cr2+complexes in the near-electrode layer is the reaction's slow stage. The experimental Tafel slope btaf= 72 mV, which is close to theoretical value of 60 mV, and the reaction orders \(P_{{\text{H}}^{\text{ + }} } \) = –1 and \(P_{{\text{Cr}}^{{\text{3 + }}} } \) = 1 are explained.

Animal–resistant telecommunication cable sheath covered by a thin hard metal layer

AbstractAerial cable lines running in forests are often damaged by animals. This paper introduces an animal‐resistant cable design by analyses of the fracture of metals when a shearing force is applied. As a result of the analyses, it is understood that when shearing forces are applied repeatedly to a metal plate without strain relaxation (similar to the case in which animals attack the cables), the metal does not fracture as long as the shearing energy is below a critical energy. This critical energy can be estimated from tensile strain at the yield point and the tensile stress at the fracture point. Therefore, it is possible to realize an animal‐resistant metal sheath by making the critical energy higher than the shearing energy which an animal can apply on one impact. It was found that the animal‐resistant cable designed and fabricated by this method could withstand animal attacks.

Application of chromium carbide hard-metal layers to steel parts by hot press-facing

Application of chromium carbide hard-metal layers to steel parts by hot press-facing