Development of quality control and structure parameters determination methods for large size products from sintered hard alloys WC-(Co+Ni+Cr) based on analysis of the ultrasonic oscillations spreading parameters

The object of research is hard alloys with a morphology of the carbide phase skeleton structure, in which particles contact with each other, and the gaps between them are filled with a binder phase. The mechanical and service characteristics of such materials depend on the degree of development of the skeleton structure. One of the most problematic areas is the lack of non-destructive methods for determining the parameters of the structure. The introduction of such techniques will allow obtaining objective information on the structure of the material and using it to evaluate the quality of products. In the course of the study, the parameters of the scattering of elastic vibrations in inhomogeneous media were determined. The main hypothesis of the study is the assumption that the processes of energy dissipation occur both in the structural elements themselves (carbide grains and bond areas) and at their boundaries. Therefore, the evaluation of dissipation processes will allow obtaining a quantitative estimation of the alloys structure parameters, and will allow assessing the quality of the material. The following characteristics were chosen as the parameters characterizing the propagation of ultrasonic oscillations: the speed of the oscillations propagation, the scattering background level in relation to the amplitude of the bottom reflection, the oscillations attenuation coefficient. The parameters were determined and compared with the characteristics of the quality of the products and the parameters of the microstructure, which were determined by the methods of quantitative metallography and the statistical characteristics of the relationship between the parameters, were determined. As a result, new quality control procedures for carbide products have been developed. The contiguity characteristics of the carbide skeleton of the sintered cemented carbide were determined by measuring the propagation speed of ultrasonic oscillations. The assessment of the level of porosity with a pore size of less than 1 mm was carried out according to the results of measuring the relative amplitude of the background scattering of ultrasonic oscillations. The proposed methods are non-destructive and are carried out in one cycle with ultrasonic flaw detection, to which 100% of the products are subjected. These techniques have been introduced in the production of carbide rolls by the method of controlled hot vacuum pressing. They have become an integral part of the quality control system for carbide rolls.

Ultrasonic oscillations induced property development of water-bentonite suspension containing sulfonated wood coal

During drilling fluid preparation, ultrasonic oscillations were introduced into water-bentonite suspension incorporating sulfonated wood coal (SMC) by a specially designed device. The influences of ultrasonic oscillations on fluid loss and rheological performances of the drilling fluid as well as mechanism of ultrasonic action were investigated. The experimental results showed that the filtrate volume decreased with the increase of ultrasonic time till a certain extent and then leveled off. In the presence of ultrasound, shorter time of 15 min and mild intensity of 250 W could lead to a satisfactory result in fluid loss properties, including the reasonable filtrate volume and thin and compact filter cakes. With increasing ultrasonic intensity, the fluid loss properties changed relatively little but various rheological data of the drilling fluids always increased. Adsorption tests through total organic carbon, infrared spectrum and thermogravimetic analyses as well as clay particle size analysis confirmed that as compared with the conventional agitation, ultrasound-assisted mud preparation could not only increase adsorbed amount of SMC on bentonite but also decrease average clay particle diameter attributed to acoustic cavitation. A plausible mechanism based on sonochemical thermodynamics is proposed to explain the improvement of the colloidal structure and performances of drilling fluid.

IMPROVEMENT OF METHOD FOR PRODUCING CHEMICAL ABSORBER OF AMMONIA AND HYDROGEN SULFIDE

The method of obtaining a chemical adsorbent of ammonia and hydrogen sulfide is proposed to be modified to improve sorption characteristics. The dependence of the kinetics of the process was studied - crystallization of solutions of copper (II) sulfate with a concentration of 2.19 mol/dm3 and 2.38 mol/dm3 depending on the method of preparation of the impregnating solution: thermal with heating to a temperature of 80 - 90 °C, using ultrasonic oscillations with a frequency of 22 kHz and an intensity of 3.5 W/cm2, and the dependence of the studied thermal method with the additional introduction of 0.01% surfactants into the solution with nonionic, anionic and cationogenic properties. Crystallization of copper sulfate was performed using a probe video microscopy system. The formation of smaller crystals is observed upon cooling of the solutions subjected to ultrasound. The introduction of surfactants did not affect the size of the crystals of copper (II) sulfate. The dependence of the physicochemical properties of a solution of copper (II) sulfate at a concentration of 1.17 mol/dm3 and 2.26 mol/dm3 on the introduction of 0.01% surfactant and a change in the temperature of the solution was studied. It was found that the introduction of a surfactant can effectively reduce the surface tension of the solution at a temperature of 80 °C and reduce the contact angle of the solution of activated carbon granules. Impregnating solutions of copper (II) sulfate are prepared using the above methods and samples of a chemical adsorbent of ammonia and hydrogen sulfide are made by impregnating granular activated carbon with the obtained solutions. It is proved that the use of surfactants and ultrasonic vibrations during the preparation of an impregnating solution allows to increase the amount of active form of copper on the surface of the carrier during impregnation, which helps to increase the dynamic capacity of chemisorbents.

Study on Influence of a State of Dopants on Dislocation-Dopant Ions Interaction in Annealed Crystals

Combination method of strain-rate cycling tests and application of ultrasonic oscillations was conducted for KCl:Sr2+ (0.035, 0.050, 0.065 mol.% in the melt) single crystals at low temperatures. The measurement of strain-rate sensitivity (λ) of flow stress under the application of ultrasonic oscillatory stress provides useful information on the interaction between a mobile dislocation and impurities (Sr2+ ions) during plastic deformation and the variation of λ with stress decrement (Δτ) due to oscillation has stair-like shape: The first plateau place ranges below the first bending point (τp1) at low stress decrement and the second one extends from the second bending point (τp2) at high stress decrement. The value of λ decreases with the Δτ between the two bending points. The τp1 is considered to represent the effective stress due to impurities when a dislocation begins to break-away from the impurities with the help of thermal activation during plastic deformation. Annealing the impure crystal by heat treatment, τp1 decreases obviously at low temperature and the critical temperature Tc, at which τp1 is zero, also becomes slightly smaller. Furthermore, it was investigated whether a change in the state of a small amount of impurities has an influential factor of the flow parameters (e.g., the activation energy, the density of forest dislocations) from the data analyzed in terms of Δτ vs. λ curve.

Improvement of Removal Rate of Tape Lapping by Applying Fluid with Ultrasonic Excited Cavitation

Lapping with a lapping tape refers to a finishing process in which a new tape is continuously supplied to its processing area and pressed down with a pressure roller during its relative motions. In response to the growing demand for lapping high-hardness materials with high efficiency, lapping tapes with superabrasive grains formed in a textured structure with a bond have been recently utilized. In this study, we supply a working fluid that has passed through the slit between ultrasonically oscillating blades to processing points. Variations of sound pressure generate cavitation in the working fluid. Impulse waves due to the collapse of cavitation bubbles inhibit chips from getting adhered to the chip pockets of the lapping tape. We have lapped hardened SUJ2 with plural lapping tapes of different characteristics. In lapping with a lapping tape using diamond abrasive grains, we have improved the time constant for the changes in surface roughness in relation to the lapping time from 18.9 s to 7.6 s by superimposing ultrasonic oscillations; consequently, the lapping speed improved. We have compared the effects of ultrasonic oscillations for three types of lapping tapes and discovered that fewer abrasive grains and lower chip adhesion firmness due to the abrasive grains formed in a textured structure increased the effects of ultrasonic oscillations.

INTENSIFICATION OF MIXING OF HETEROGENEOUS FOOD MIXTURES UNDER THE IMPACT OF ULTRASONIC VIBRATIONS

There is known equipment for mixing of heterogeneous food mixtures analyzed in this article. Some part of this equipment provides qualitative mixing at macro-level (mixing of large portions of processed material), for example, paddle, propeller, turbine, anchor, screw, gravitation and drum mixers. Another part of mixing machines on the contrary, allows to achieve of effective micro-level mixing (mutual movements of adjacent particles of material) – vibratory and centrifugal mixers. In some cases there is important to provide well mixing both at macro- and at micro-level, when it is accompanied by thermal, diffusion or chemical processes and from its efficiency depend energy expenses and qualitative characteristics of product. Therefore, a task of elaboration of schemes of improved apparatuses for effective macro- and micro-mixing of dry and liquid multi-component food materials is resolved in the article. Authors are proposing to create these apparatuses at the base of well known equipment – gravitation and screw mixers by way of their additional equipping with serial electromagnetic vibro-exciters of ultrasonic oscillations. As a result, a main drive of a base mixer will provide working process at macro-level and an additional drive – micro-level movements of material particles. The proposed apparatuses have a simple and reliable construction, don’t consist of original parts and at the same time, provide necessary efficiency of working process. Equations of movements of processed components particles in course of their different loading stages, with examination of physical-mechanical properties of the components are also presented in the article. These equations can be used as a base for further creation of methods of design calculation of proposed apparatuses.