Roughness measurement as an alternative method in evaluation of cavitation resistance of steels

The purpose of this study was to investigate possible application of roughness measurement in evaluation of resistance of steels in conditions of cavitation effect where these materials are usually applied. Steels which belong to different classes were selected for testing. Cavitation testing was performed by using the ultrasonic vibratory cavitation test set up (stationary specimen method). Mass loss and surface degradation of investigated samples were monitored during the exposure to cavitation erosion. Mass loss was measured by an analytical balance. The morphology of the damaged surfaces with the change of the test period was analyzed using scanning electron microscopy (SEM). The surface roughness tester was used to monitor changes of surface roughness during the test and for obtaining the line profile of surface samples after cavitation tests. Cross-sections of samples were made after testing and optical microscopy was used to obtain complete information about the roughness change and compare the images with the lines of the profile obtained by the measurement of roughness. It can be concluded that the behaviour of steels under conditions of cavitation can be estimated by measuring the change in surface roughness. Conclusions adopted on the basis of roughness changes are consistent with that based on measurements of mass loss and morphology of surface damage during cavitation testing time

Cavitation resistance of basalt-based protective coatings and epoxy system

The paper presents the results of synthesis and characterization of new refractory coatings based on basalt and epoxy system. Coatings are intended to protect the surfaces of parts of equipment and various structures in civil and mechanical engineering and metallurgy which are exposed to wear, corrosion, or cavitation during exploitation. Coating composition, procedures for preparation of components from coating composition, synthesis procedures, and application of coatings are investigated. Several methods are used to characterize the coating: X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), optical microscopy and ultrasonic vibration method with a stationary sample according to ASTM G32 standard. Material resistance to the action of cavitation is determined using the ultrasonic method. In order to monitor the formation and development of surface damage on samples under the effect of cavitation, the morphology of surface coating damage is analysed using scanning electron microscopy. Results show high resistance of the tested basalt-based coatings under the action of cavitation, with low cavitation rate (0.04 mg/min), low mass losses of coating and minor surface damage during exposure. This indicates the possibility of applying this type of refractory coating for the protection of various metallic and non-metallic structures in conditions of wear and cavitation

Cavitation Properties of Rendering Mortars with Micro Silica Addition

Micro-silica is a highly efficient mineral additive whose role is reflected in improvements of microstructure packing, strength and durability of non-shaped composite building materials such as concrete and mortar. A comparative study of performances of rendering mortars with different quantities of micro silica was conducted. The experimental program included production of reference mortar based on Portland cement and quartz sand (CM) and three mortars with 5, 10, and 15 % addition of micro silica (SCM-5, SCM-10, and SCM-15). The effect that micro silica addition has on the thermal behavior and mechanical properties of mortars was discussed. Hydration mechanisms and thermally induced reactions were studied at temperatures ranging from ambient to 1100 degrees C by differential thermal analysis. The results were supported by X-ray diffraction analysis. The cementing efficiency of micro silica was assessed by cavitation erosion test. The changes in the morphology of mortar samples prior and upon cavitation testing were monitored by means of the scanning electron microscope imagining. It was found that 5 % of superfine micro silica (SCM-5 mortar) has positive effects on mechanical strengths (15 % increase in compressive strength) due to microstructure densification arising from the successive filling of voids by the micro silica. Addition of micro silica also improved the cavitation erosion resistance in comparison with reference cement mortar (SCM-5 showed cavitation velocity as low as 0.09 mg/min). This qualifies mortars with micro silica addition as building materials which can be safely employed in potential hydro-demolition environment

Cavitation Wear of Basalt-Based Glass Ceramic

This paper examines the possibility of using basalt-based glass ceramics for construction of structural parts of equipment in metallurgy and mining. An ultrasonic vibration method with a stationary sample pursuant to the ASTM G32 standard was used to evaluate the possibility of the glass ceramic samples application in such operating conditions. As the starting material for synthesis of samples, olivine–pyroxene basalt from the locality Vrelo–Kopaonik Mountain (Serbia) was used. In order to obtain pre-determined structure and properties of basalt-based glass ceramics, raw material preparation methods through the sample crushing, grinding, and mechanical activation processes have been examined together with sample synthesis by means of melting, casting, and thermal treatment applied for the samples concerned. The mass loss of samples in function of the cavitation time was monitored. Sample surface degradation level was quantified using the image analysis. During the test, changes in sample morphology were monitored by means of the scanning electronic microscopy method. The results showed that basalt-based glass ceramics are highly resistant to cavitation wear and can be used in similar exploitation conditions as a substitute for other metal materials

Reuse potential of functionalized thermoplastic waste as reinforcement for thermoset polymers: Mechanical properties and erosion resistance

Two types of polymer waste materials, poly(ethylene terephthalate) (PET) and polycarbonate based Colombian Resin (CR-39), were used for the designing of fully recycled composite materials. Waste PET was employed for the synthesis of thermoset unsaturated polyester resin (UPR), while CR-39 was used as reinforcement in the UPR matrix. Prior to mixing, CR-39 particles were subjected to oxidation and chemical activation using acids/base and ethanol amine, respectively. The effect of the modifier type and variable loading of the activated CR-39 particles on mechanical and dynamic-mechanical properties of the corresponding composites was investigated. The greatest improvement in the tensile and flexural strength of UPR resin was achieved with the composite containing 0.5 wt% of amine activated filler particles, 96.0% and 62.2%, respectively. The Arrhenius equation was used to calculate the activation energy for glass transition from dynamic mechanical properties measured at various frequencies. The activation energy of the main transition for UPR resin and composites were calculated to be 173 and 350 kJ center dot mol(-1) indicating that reinforcement results in an increase in the energy barrier to macromolecules viscoelastic relaxation. In addition, erosion resistance was studied during exposure of samples to cavitation tests. According to the obtained results, these materials can be applied in construction and mining industry

Non destructive monitoring of cavitation erosion of cordierite based coatings

Coating materials are widely used in refractory lining to prevent different deleterious effects such are reactions on the mold-metal contact surface, abrasion from liquid metal or alloy, gasses, slags, and other materials in contact with the coating. In this paper, behavior of cordierite based coating exposed to the cavitation erosion was investigated. Cordierite samples sintered at 1200 and 1400 degrees C were used for the tests. Mass loss, level of surface degradation obtained using image analysis and thermal imaging analysis were applied for the cavitation erosion evaluation. Results showed that the cordierite samples can be successfully used in conditions where the cavitation resistance is required

Optimization of modifier deposition on the alumina surface to enhance mechanical properties and cavitation resistance

Composites based on poly(methyl methacrylate), dimethyl itaconate matrix and alumina particles were prepared. Ferrous oxide-doped alumina particles (Al2O3Fe) and commercial alumina nanoparticles (Al(2)O(3)n) modified with (3-aminopropyl)trimethoxysilane (AM) and methyl esters of linseed oil fatty acids (biodiesel-BD) were used as reinforcement. The mechanical properties of the prepared composites, containing 1, 3 and 5 wt% of surface-modified alumina particles, are compared to a neat polymer matrix. The particles were characterized by single-beam Fourier transform infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The mechanical properties of the composites were determined by micro-Vickers hardness and impact testing. The morphology of the surface of the composites exposed to cavitation was observed through a field emission scanning electron microscope. AFM analysis was used to compare surface features seen using the SEM and to interpret the surface degradation properties. The hardness, cavitation resistance and high-impact energy resistance of the composites are better in the case of AM surface modification of alumina fillers, but biodiesel modified particles have comparable mechanical properties and a stabilized Al-O-Si bond that could be important when a composite is exposed to humidity or a wet environment