Thermally sprayed alumina coatings are widely used in a range of industrial applications to improve wear and erosion resistance, corrosion protection and thermal insulation of metallic surfaces. ...These properties are required for many components to be used for production processes in the paper and printing industry.
Another appropriate method to produce ceramic coatings is the plasma electrolytic oxidation (PEO). However PEO can only be applied on self-passivating metals like aluminium, titanium, magnesium and their alloys. The present paper concerns a combination of cost-efficient arc spraying and flame spraying of Al coatings (Al99.5, AlCu4Mg1) on steel substrates and post-treatment by plasma-electrolytic oxidation (PEO). The microstructure and phase composition of generated oxide coatings are examined and discussed. The created Al2O3 layers show outstanding hardness up to 1600 HV0.1, good bonding strength and excellent abrasion resistance compared to atmospheric plasma-sprayed Al2O3-coatings. The results show the superior performance of PEO-coatings and demonstrate their applicability for technical components in extreme operating conditions.
Abstract
High-entropy alloys (HEAs) provide advanced properties like a high resistance to corrosion and wear. Concerning this and the elevated material costs wear protection layers are a possible ...field of application. Finish machining of these layers is necessary to achieve adequate surface properties. In the experimental investigations face turning of high-entropy alloy CoCrFeNi layers generated by spark plasma sintering is regarded. In this context, the influence of the cutting material and the cutting speed is analysed. For this, CBN tipped (two types), PCD tipped, CVD diamond tipped, and solid cemented carbide indexable inserts are used. Additionally, the influence of four different cutting speeds in the range between 100 m/min and 400 m/min is analysed. The feed and the depth of cut are kept constant with 0.05 mm and 0.1 mm, respectively. The geometrical surface properties are determined by tactile measurements and 3D laser scanning microscopy. The tool wear is analysed microscopically. Regarding the surface roughness, CBN tipped tools with a high content of boron nitride lead to the best results with the lowest roughness values irrespective of the cutting speed. The tool wear is also significantly reduced compared to the other cutting materials tested. The investigations represent the first results analysing the influence of the cutting material in machining of high-entropy alloys. Hence, this contributes to the enhancement of the field of application of HEAs.
This contribution deals with the determination of the mechanical and thermal properties of thermally sprayed materials. To this end, a comprehensive characterization of copper (Cu 98.7) and ...corrosion-resistant steel (316L) is carried out by temperature-dependent tensile, three-point bending and caloric tests within a temperature range from 293 K up to 1173 K. For this purpose, thick coatings were manufactured by wire arc spraying. The resulting volume was further processed by electrical discharge machining into suitable test samples. Reference specimens from the corresponding solid materials were also tested for evaluating the morphological features of the coatings. During the calorimetric examinations, the thermally applied materials were exposed to temperatures of up to 1173 K. As a result, permanent property changes could be observed. To investigate these heat treatment effects, metallographic preparations and XRD analyses were performed. Based on the results, conclusions on the morphology of the thermally applied materials could be drawn.
Coordination complexes M(O
CCH
OC
H
OMe)
(M = Co, 4; M = Mn, 5) are accessible by the anion exchange reaction between the corresponding metal acetates M(OAc)
(H
O)
(M = Co, 1; M = Mn, 2) and the ...carboxylic acid HO
CCH
OC
H
OMe (3). IR spectroscopy confirms the chelating or μ-bridging binding mode of the carboxylato ligands to M(ii). The molecular structure of 5 in the solid state confirms a distorted octahedral arrangement at Mn(ii), setup by the two carboxylato ligands including their α-ether oxygen atoms, resulting in an overall two-dimensional coordination network. The thermal decomposition behavior of 4 and 5 was studied by TG-MS, revealing that decarboxylation occurs initially giving M(CH
OC
H
OMe)
, which further decomposes by M-C, C-O and C-C bond cleavages. Complexes 4 and 5 were used as CCVD (combustion chemical vapour deposition) precursors for the deposition of Co
O
, crystalline Mn
O
and amorphous Mn
O
thin films on silicon and glass substrates. The deposition experiments were carried out using three different precursor solutions (0.4, 0.6 and 0.8 M) at 400 °C. Depending on the precursor concentration, particulated layers were obtained as evidenced by SEM. The layer thicknesses range from 32 to 170 nm. The rms roughness of the respective films was determined by AFM, displaying that the higher the precursor concentration, the rougher the Co
O
surface is (17.4-43.8 nm), while the manganese oxide films are almost similar (6.2-9.8 nm).
Motivated by the improvement of the cost and resource efficiency of the manufacturing process of age-hardening aluminum components, the influence of an initial heat-treatment, prior to plastic ...deformation, on the artificial aging behavior and the hardness is investigated. Systematic work is done by comparing three initial heat-treatment conditions of the age-hardening aluminum alloy 6056 prior to low-temperature plastic deformation: a solid-solution heat-treated, a naturally aged and a stabilized one. Two plastic deformation processes, linear extrusion and compression, each with two different strains, respectively, were performed and followed by artificial aging. The hardness was measured prior to plastic deformation as a function of the natural aging time, and after plastic deformation as a function of the artificial aging time. Stabilization annealing of the aluminum alloy inhibited natural aging. After plastic deformation and artificial aging, the stabilized conditions showed an increased hardness, as compared to the solid-solution heat-treated, respectively naturally aged, condition. The artificial aging behavior of all tested conditions was only slightly influenced by the respective plastic deformation process. However, the hardness was similar for the extruded, respectively compressed, conditions in their respective initial heat-treatment conditions.
The lap shear test is a common method for determining the interlaminar shear strength of material compounds due to its simplicity with regard to specimen production and experimental realization. ...However, the obtained results strongly depend on the material pairing and the specimen geometry, which have a significant influence to the stress state within the interface during the experiment. A torsion test method using butt-bonded hollow cylinders seems more appropriate due to the expected more homogeneous shear stress distribution. The aim of this work is to compare both testing methods by experimental and numerical investigations. A comparative study with thermally joined aluminum-polyamide hybrid compounds was performed. The corresponding simulations were carried out with the commercial FE-software Abaqus™, using a user defined material model for the thermoplastic joining partner and the built-in cohesive behavior contact property for modelling interfacial damage.
The age-hardenable aluminium alloy EN AW-7075 exhibits outstanding specific mechanical properties and therefore offers a high potential for lightweight construction. Anodising in aqueous oxalic acid ...solutions is suitable to produce a protective oxide ceramic conversion layer on this alloy. This study examines the influence of the precipitation state of the substrate alloy on microstructure and properties of anodic oxide layers. Therefore, EN AW-7075 sheets in the heat treatment conditions T4, T6 and T73 were anodized in 0.8 M oxalic acid solution at constant voltage. The current efficiency was determined on the basis of the electrical charge quantity, coating thickness and coating mass. Instrumented indentation tests were applied in order to evaluate the coating hardness. The microstructure of the anodic oxide layer was illustrated using field emission electron microscopy. It was shown that the current efficiency strongly depends on the heat treatment condition.
The warm deformation behavior of a β-type Ti alloys, composing of Ti–27.96Nb–11.97Ta–5.02Zr %wt, (so called TNTZ alloy), has been investigated in the present work in a warm deformation temperature. A ...variety of deformation features are characterized in the material microstructure after applied warm deformation scheme. The XRD analysis confirms an enhancement in martensite volume fraction. The electron back scatter diffractometry (EBSD) elucidates that the martensite has been mainly formed by laterally at the vicinity of different types of deformation bands. Both the well-known twining systems in TNTZ series have been occurred during deformation. The micro-shear bands, which are defined as highly concentrated plastic strain regions, are characterized in the deformed microstructure. The micro-shear bands are severely formed in the regions, which accommodate the most amount of applied strain.
The coupled temperature–strain rate sensitivity (SRS) of Ti–29Nb–13Ta–4.6Zr β-type Ti-alloy has been studied. The martensitic transformation is identified as the main reason of negative rate ...sensitivity during deformation at room temperature and 100°C. In addition dynamic strain aging (DSA) is in charge of further decrease in SRS values at temperatures higher than 100°C. The SRS values start increasing beyond 200°C due to dissipating the DSA effects. This finally reaches the positive domain due to domination of dislocation slip.
A process for the simultaneous plasma-electrolytic anodic oxidation (PAO) of a compound consisting of an Al (AlMgSi1) and Mg (AZ31) alloy is introduced. Using this process, an almost uniformly thick, ...compact oxide coating on both compound partners can be produced provided that the narrow window of this process is determined and kept. The most important parameters for the simultaneous plasma anodizing are the composition and conductivity of the used electrolyte, the current density and the process time. A short-time process using high current densities has been found suitable. This process is a promising procedure for the protection of Al- and Mg-based compound surfaces.
► Simultaneous PAO of a compound consisting of an Al (AlMgSi1) and Mg (AZ31) alloy. ► Production of uniformly thick, compact oxide coatings on both compound partners. ► Simultaneous PAO needs short-time processes and high current densities.
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