Key Engineering Materials Vol. 910

Abstract: The characteristics of coatings designed to protect against cavitation and waterjet wear, obtained by supersonic atmospheric plasma spraying using air as a plasma-forming gas, are studied. The following powder materials were selected for coating: WC/10Co4Cr; Ni-Cr-B-Si-C; Ni-Al; Ni-Ti; bronze. Metallographic studies of the structures of specimens with applied coatings and measurements of their microhardness were carried out. Due to the fact that the tests of materials for hydroabrasive wear are not standardized, studies were carried out on the resistance of coatings to dry abrasive wear according to the ASTM G65-04 standard and to dry reciprocating friction according to the ASTM G133 standard. The conducted studies of the structures of the sprayed coatings suggest that the use of supersonic deposition modes guarantees the production of high-density coatings with a porosity of less than 1 %.

Abstract: Polymer-based fiber composites have a number of unique physical and mechanical properties and are widely used in the design of structural elements in rocket and space engineering. However, along with the high characteristics of strength and rigidity, there is a noticeable anisotropy of properties which contributes to occurrence and development of damage leading to degradation of the load bearing capacity of structures and their premature destruction. Along with development of micromechanical and phenomenological models, an important place has the procedure for identifying the basic characteristics of composite materials. Such characteristics, in particular, include those of layer elasticity which are usually used when designing structures. However, even such characteristics depend on the loading conditions and for their identification, computational methods based on statistical analysis should be used. This paper attempts to identify the elastic characteristics based on test results of unidirectional carbon plastic with AS4 carbon fibers and polyetheretherketone thermoplastic matrix. For identification, the least squares method was used for samples tested at off-axis angles of 0, 10, 30, 45, 60 and 90 ° and different values of strain rates.

Abstract: The stability of rectangular thin plates of Shape Memory Alloys during the forward martensitic phase transition induced by uniform cooling under constant stresses was studied. A model of the constitutive equations of Shape Memory Alloys describing phase structural deformation and taking into account thermomechanical coupling and resistance asymmetry was used. It was shown within the limits of this model that the structural deformation during the loss of stability could not occur. Analytical solutions obtained for different statements of the stability problem were compared. For some statements the curves separating the areas of stability and instability in the plane of stresses had concave parts were obtained. It was shown that increase of the plate thickness brought about rising the influence of the phase deformation on the stability loss process.

Abstract: Dynamic tests of new magnetoactive elastomers were carried out in various amplitude-frequency modes on vibrodynamic stands. These materials regular changes in resonance properties under the external constant magnetic fields and loads influence have been established. The relationship between vibrodynamic and damping properties in these composites and atomic force microscopy data on the magnetic fillers restructuring under magnetic field action in a silicone elastomers matrix is discussed.

Abstract: The results of the experimental study of the mechanical properties and structure of the Co-9.5Al-2.9Mo-4Nb, Co-9.1Al-5.2Mo-4.7Nb, and Co-8.9Al-6.5Mo-9.3Nb alloys were presented. The Young’s moduli in the studied alloy samples were found to be smaller than those of Ni₃Al-based and Co₃(Al,W)-based alloys. The eutectic structure was observed in all studied alloys. Cuboids of the Co₃(Al,Nb,Mo) intermetallic compound with L1₂ crystal structure were found by TEM study.

Abstract: In this work, the evolution of the microstructure, phase composition and crystal structure of 3D products before and after heat treatment, obtained from the original steel 12Cr18Ni10Ti by various metallurgical methods of melting, was studied. The obtained 3D steel samples were subjected to heat treatment, then structural changes were investigated by metallography, X-ray phase (XRD) and X-ray structure (XRD) analyzes. The analysis showed that heat treatment did not increase the grain size of austenite in additive steels, but could lead to an increase in the proportion of ferrite.

Abstract: The paper presents the results of development and study of a composite powder of Ti-TiB₂ system. Comprehensive studies of composite coatings formed by microplasma spraying of the developed powders are carried out. It is determined that the developed composite materials are promising for use in elements and friction units of wind power plants and shipbuilding engineering objects.

Abstract: Electron beam processing was considered to be the promising modification method for Al-Mg alloys. An investigation of the effect of high energy density on the surface modification layer was developed. The results demonstrated that the grain boundaries emerged and there are some microcracks formed along grain boundaries due to superfast heating and cooling speed during the treatment process. Due to this special microstructure morphology, the average friction coefficient was decreased but the wear volume was increased, and the yield strength and the ultimate tensile strength are reduced.