Microhardness Values Research Articles

Comparison in microstructure, mechanical properties, and fatigue behavior of 9Cr3W3Co turbine rotor steel and its welded joint

AbstractThe microstructure, mechanical properties, and high/very‐high cycle fatigue behaviors of 9Cr3W3Co turbine rotor steel and its welded joint were investigated. The welded nugget zone (WNZ) exhibited the highest microhardness value, followed by the heat‐affected zone (HAZ), while the base material (BM) showed the lowest hardness value. The WNZ exhibited a higher yield strength compared to the BM with reduced elongation, while maintaining similar ultimate tensile strength. The fatigue strength of the BM at 5 × 107 cycles is roughly 53.7% of the yield strength, whereas that of the WNZ increases to approximately 55.0%. In comparison to the fatigue strength of the BM at 5 × 107 cycles, the WNZ exhibits a notable increase of 10.5%. Smaller grain size and higher dislocation density were observed in the WNZ, which contributed to improved microhardness, yield strength, and fatigue resistance through grain boundary strengthening and dislocation hardening.

Investigating the Impact of Friction Stir Processing on the Hydrogen Embrittlement in AA6082-T6 Heat-Treatable Aluminum Alloy

AbstractThis study investigates the impact of friction stir processing (FSP) on the hydrogen embrittlement (HE) in AA6082-T6 heat-treatable aluminum alloy. The effects of different number of FSP passes and different hydrogen cathodic charging (HCC) conditions on the material’s response to HE are examined through comprehensive mechanical testing, microhardness analysis, and microstructural characterization. The results revealed that FSP leads to a decrease in yield strength, ultimate tensile strength, and microhardness, accompanied by an increase in energy absorption. The introduction of hydrogen through HCC significantly reduces mechanical properties, particularly in non-FSPed specimens. Notably, specimens with 8 FSP passes exhibit an interesting behavior with a slight increase in energy absorption and microhardness values after HCC. Microstructural analysis shows that FSP refines the microstructure, resulting in enhanced resistance to hydrogen-induced blistering effects. These findings contribute to the understanding of hydrogen embrittlement in FSPed aluminum alloys, providing insights for developing surface-modified materials suited for hydrogen-rich applications. Graphical Abstract

Planning Mechanical Behavior of A356 Alloy Wheels by Using Distinct Heat Treatments

The aim of this investigation concerns evaluating the mechanical strength and microhardness values of A356 alloy samples in distinctive heat treatments, including those commonly applied to automotive wheels. It is recognized that A356 and Al-Si-based alloys exhibit considerable versatility across numerous industrial applications. The mechanical behavior obtained is intimately associated with different operational parameters (e.g., cooling rates, solution treatment, quenching, and artificial aging). In this study, a group of samples are quenched at 30, 60 and 80 °C. Another set is quenched and subsequently aged at three different temperatures, i.e., 180, 200, and 220 °C for 5 h, and mechanical responses are compared. Microstructural characterization, X-ray diffraction (XRD) analysis, tensile testing, and microhardness measurements are carried out. Using the Rietveld data and based on the modified Williamson–Hall method, the microstrains, crystallite size, and dislocation densities are calculated. Based on this, the resulting mechanical strengths from distinctive quenching and aging are understood. It was found that there exists a “quasi-optimal range” of operational parameters involving different A356 alloy treatments, which vary depending on the manufacturing route. Considering A356 alloy wheels, the planning of the powder coat treatment before or after T6 treating provides better mechanical properties and ductility.

Evaluation of 3D Printing Orientation on Volume Parameters and Mechanical Properties of As-Build TI64ELI

The discovery of the utility of various titanium alloys as implant biomaterials has resulted in these materials becoming far more popular than other metals in the medical world. However, the production of these materials using additive manufacturing has its own challenges some of those being the surface finish that can be used as an implantology material. As such, the purpose of this study is to evaluate the influence of 3D-printed Ti64ELI on the as-built samples printed at 60°, 90°, and 180° orientations. Such studies are very limited, specifically in the development of the laser shock peening surface modification of dental implants. The study showed that each mechanical test that was performed contributes differently to the printing orientation, e.g., some tests yielded better properties when 180° printing orientation was used, and others had poorer properties when a 180° printing orientation was used. It was observed that 60° testing yielded a micro-hardness value of 349.6, and this value was increased by 0.37% when 90° orientation was measured. The lowest HV value was observed under a 180° orientation with 342.2 HV. The core material volume (Vmc) was 0.05266 mm3/mm2 at a 60° orientation, which increased by 11.48% for the 90° orientation. Furthermore, it was observed that the surface roughness (Sa) at 60° orientation was 43.68 μm. This was further increased by 6% when using the 90° orientation.

The erosive effect of pomegranate juice on enamel: An in vitro study.

Dental erosion is a chemical-mechanical process that leads to the loss of dental hard tissues. This study aimed to investigate the effect of pomegranate juice on the enamel. Enamel blocks were randomly divided into three groups: deionized water, cola, and pomegranate juice. The blocks were immersed in the solutions four times a day for 14 days, and stored in artificial saliva for the remaining period. The surface hardness was measured on days 7 and 14. The surface structures of the demineralized blocks were observed via scanning electron microscopy (SEM), and the depth of demineralization was observed via confocal laser scanning microscopy (CLSM). The pH, calcium, and phosphorus levels of the three solutions were analyzed. The microhardness values of the blocks in the pomegranate juice and cola groups decreased with the increase in the demineralization time. The blocks in the pomegranate juice group exhibited large fractures in the enamel column, whereas those in the cola group had pitted enamels with destruction of the interstitial enamel column. Compared with cola group, fluorescent penetration increased in pomegranate juice (P < 0.01). The pH of cola (2.32 ± 0.09) was lower than that of pomegranate juice (3.16 ± 0.16). Furthermore, the calcium content in pomegranate juice was significantly higher than that in cola (P < 0.01). Alternatively, the concentration of phosphorous in cola was significantly higher than that in pomegranate juice (P < 0.01). These findings indicate that pomegranate juice can cause enamel demineralization with an erosive potential comparable to that of cola.

Comparative evaluation of effect of modified triple antibiotic paste and calcium hydroxide as intracanal medicament on microhardness of root dentin: An in vitro study

ABSTRACT Aim: To assess and compare the impact of modified triple antibiotic paste (MTAP) and calcium hydroxide (CH) as intracanal medicament on microhardness (MH) of root dentin. Materials and Methods: Twenty single-rooted, noncarious, single-canaled permanent teeth were selected. They were decoronated and vertically sectioned into two equal parts to acquire 40 samples. These samples were submerged in acrylic blocks with their pulpal surfaces exposed. These samples were enclosed within acrylic blocks, with their pulp surfaces visible. They were then randomly allocated into four groups (n = 10). MH was measured at three steps: initial measurement of MH before irrigation with 3% sodium hypochlorite (NaOCl); after irrigation with 3% NaOCl; and after interaction with medications (MTAP or CH pastes at an interval of 7 days or 30 days). The degree of reduction in MH percentage was computed. The collected data underwent statistical examination at a significance threshold of P &lt; 0.05. Results: All procedures led to a noteworthy decline in MH values when compared to both prior and initial measurement. The highest reduction in MH was seen after irrigation with 3% NaOCl (P &lt; 0.05). CH showed a greater reduction in MH as compared to MTAP (P &lt; 0.05). More reduction in MH was seen after 30 days as compared to that after 7 days for both CH and MTAP (P &lt; 0.05). Conclusion: Use of intracanal irrigants and medicaments reduces the MH of root dentin. Lesser reduction in MH was observed when utilization of MTAP as compared to CH.

In-situ monitoring of additive friction stir deposition of AA6061: Effect of layer thickness on the microstructure and mechanical properties

Depositions of AA6061 aluminum alloy with different thicknesses (0.5, 1.0 and 1.5mm) and homogeneous microstructure were successfully obtained through additive friction stir deposition (AFSD) technique. A self-developed in-situ process monitoring kit has been utilized to in-situ monitor the real-time temperature, force and torque during the AFSD process. Effect of thickness on the microstructure and mechanical properties are investigated based on the monitored parameters. With the electron back scattered diffraction (EBSD) analysis on a large area (4 × 4 mm2), the synergism of dynamic recrystallization (DRX) and shear deformation is found to affect the microstructure. DRX is the main reason for the grains refinement which are remarkably reduced to 7 μm as the thickness increases. Whereas, the shear deformation exhibits a stronger effect on the texture. The texture intensity reduces and then increases as the thickness increases from 0.5 to 1.5mm. Values of micro-hardness (46.8 HV0.5), yield strength (106.0MPa) and ultimate tensile strength (171.2MPa) of the deposition are the highest when the thickness is the largest (1.5mm) attributed to the lowest thermal cycle and evolution of DRX. All the findings provide useful guidance for the visualization and understanding of AFSD process.

Structural, elastic, thermo-physical and gamma radiation shielding efficiency of MnO2 doped TeO2-PbO-ZnO glasses

This paper presents the fabrication of glasses with chemical formula [(TeO2)0.70 – (ZnO)0.22 – (PbO)0.08] 1-x (MnO2)x where x = 0.02, 0.04, 0.06, 0.08 and 0.1 using melt quenching technique. The main objective is to explore the structural, elastic and gamma ray shielding efficiency of the glasses. The study was conducted using density and molar volume measurements, X-ray diffraction analysis, Fourier transform infrared analysis, non-destructive ultrasonic analysis, and theoretical assessment of the glasses’ gamma ray shielding efficiency using the Phy-X/PSD software. High density values in the range of 5.611–5.735 gcm−3 and the XRD analysis showed no sharp peak indicating the amorphous nature of the glasses. The FTIR spectra revealed the presence of both TeO3 and TeO4 structural units. The values of the elastic moduli microhardness, Debye and softening temperatures, acoustic impedance, diffusion constant, Thermal expansion coefficient and latent heat of melting were studied and discussed among others. Efficiency parameters of radiation shielding such as the coefficients of mass and linear attenuation, effective atomic number, half and tenth value layers, mean free path and effective electron density were calculated theoretically and discussed. Based on the results discussed, the studied MnO2 doped TeO2-PbO-ZnO glasses appeared to be mechanically strong, and thermally stable for radiation shielding applications. Moreso, the glasses appeared to be better in terms of radiation shielding efficiency than commercial concrete materials like serpentine, barite, ferrite, and chromite.

A Detailed Study on using Novel LM 25 Aluminium Alloy Hybrid Metal Matrix Nanocomposite for Nuclear Applications.

This article describes the use of graphite(Gr) and boron carbide (B4C) as multiple nanoparticle reinforcements in LM25 aluminum alloy. Because boron carbide naturally absorbs neutron radiation, aluminium alloy reinforced with boron carbide metal matrix composite has gained interest in nuclear shielding applications. The primary goal of the endeavor is to create composite materials with high wear resistance, high microhardness, and high ultimate tensile strength for use in nuclear applications. Science and Technology have brought a vast change to human life. The human burden has been minimized by the use of innovation in developing new and innovative technologies. To improve the quality of human life, fresh, lightweight, and creative materials are being used, which play a vital role in science and technology and reduce the human workload. Composite materials made of metal are being used because they are lightweight. Neutron absorption, high ultimate strength, high wear resistance, high microhardness, high thermal and electrical conductivity, high vacuum environmental resistance, and low coefficient of thermal expansion under static and dynamic conditions are all demands for the hybrid metal matrix composites utilized in nuclear applications. • Stir casting is used to create the novel LM 25 aluminum alloy/graphite and boron carbide hybrid nanocomposites. • The mechanical properties such as ultimate tensile strength, yield strength, percentage of elongation, microhardness, and wear behavior are calculated. • Three analyses are performed: microstructure, worn surface analysis, and fracture analysis of the tensile specimen. • Stir casting process< • Tensile, Hardness, Wear Test • Materials Characterization - FESEM, Optical Microscopy, EDS< Results: The mechanical properties values are 308.76 MPa, 293.51 MPa, 7.8, 169.2 VHN, and 0.01854mm3/m intended for ultimate tensile strength, yield strength, percentage of elongation, microhardness, and wear behavior, respectively. This implies that the synthesized composite may be used in nuclear applications successfully. The subsequent explanation was drawn from this investigative work: • The LM 25/B4C/Gr hybrid nanocomposite was successfully manufactured by employing the stir casting technique. For nuclear shielding applications, these composites were prepared with three different weight percentages of nanoparticle reinforcements in 2,4,6% Boron carbide and constant 4 wt.% graphite. • The microhardness values of the three-hybrid nanocomposite fabricated castings were determined to be 143.4VHN, 156.7VHN, and 169.2VHN, respectively. • The hybrid nano composite's microstructure revealed that the underlying LM 25 aluminum alloy matrix's finegrained, evenly dispersed nanoparticles of graphite and boron carbide were present.<br></br> • The microtensile test was carried out and it was found that the ultimate tensile strength, yield strength and percentage of elongation values are 281.35MPa, 296.52MPa, 308.76MPa, 269.43, 274.69, 293.51 and 3.4, 5.7, 7.8 respectively.<br></br> • Deformation caused the hybrid LM 25/B4C/Gr nanocomposite to fracture in ductile mode. Dimples and cavities are seen in the fracture because of the nanoparticle reinforcements and the matrix's tight connection.<br></br> • The wear loss of nanocomposite based on the input parameter applied load, sliding velocity and sliding distance values are 0.02456, 0.02189, 0.01854, 0.02892, 0.02586, 0.02315 and 0.02682, 0.02254, 0.02015 mm3/m, respectively.<br></br> • The LM 25 alloy's elemental analysis displays the aluminum alloy phase as the largest peak and the remaining elements as smaller peaks; also, the spectral analysis reveals the presence of boron (B), graphite (C), silicon, and ferrous in the aluminum alloy LM 25.<br></br> • Through worn surface FESEM investigation, it was shown that under sliding and high load situations, debris, delamination, and groove develop. Further rupture, fine, and continuous grooves were seen when low stress and sliding circumstances were applied to the LM 25/B4C/Gr and stir cast specimen. This result implies the presence of mild adhesive and delamination wear processes.</P>.

BIOSOLUBLE MAGNESIUM-BASED ALLOYS FOR OSTEOSYNTHESIS

The impact of micro-alloying of AZ91 and NZ30K magnesium alloys with silver and scandium to produce biosoluble implants for osteosynthesis is studied in the paper. The application of these alloys is limited due to the significant reduction of the mechanical properties of magnesium during the regeneration of fractures.  It was found that the higher the concentration of the above-mentioned elements, the bigger the amount of intermetalloids that appear and the smaller they become. There were different mechanical properties observed at the sample cross-section, but the difference was successfully eliminated by thermal treatment. It reduced the chemical heterogeneity of the workpiece at the cross-section and, respectively, the value of micro-hardness. It is shown that microalloying these alloys with 0.05…0.1 % of silver and scandium ensures the grinding of the structural elements of the metal and a significant increase of the set of their properties. The research of the developed alloys showed that NZ30K alloy, which additionally contains 0,05 ... 0,1% of silver, after a three-month treatment with gelofusine saves its mechanical properties like those of the bone tissue. Pre-clinical research revealed that they are non-toxic, have an antibacterial effect and preserve the whole set of properties till the complete fracture consolidation.

EXPERIMENTAL STUDY AND MONITORING OF TEMPERATURE AND SURFACE ROUGHNESS AND MICRO-HARDNESS OF THE WHEEL–RAIL CONTACT IN THE DESERT REGION OF THE OUARGLA TRAMWAY

Public transport via trams has become increasingly important in daily life to meet the growing demand for economic and environmental considerations. In order to ensure the safety of the railway system and reduce service costs, it is necessary to understand the tribological behavior of the system. There are various types of damage such as fatigue, wear, and cracking that can harm the wheels and rails. To determine the wear mechanisms and identify the situations in which wear movements occur, it is crucial to monitor factors such as temperature, surface roughness, and contact micro-hardness between the wheel and the rail. The objective of this study is to analyze the tribological behavior and the impact of climatic conditions on the wheel–rail contact system in the desert area of the Ouargla tramway in Algeria. To achieve this, an intelligent sensor programmed by a microcontroller was utilized to measure the temperature of the wheel–rail contact. Additionally, a hardness tester was used to measure the micro-hardness of the rail, and a roughness tester was utilized to monitor the surface condition of the rail. The measured temperature values during the passage of the tramway varied between ambient temperature and a temperature of 450∘C. The micro-hardness values ranged from 270 Hv to 440 Hv, and the roughness values varied between 0.4[Formula: see text][Formula: see text]m and 2.7[Formula: see text][Formula: see text]m.

Effects of low-power laser hardening on the mechanical and metallurgical properties of biocompatible SAE 420 steel

The present experimental work is carried out on SAE 420 steel to optimize process parameters of low-power laser hardening to improve surface micro-hardness and wear resistance for dry sliding for bio-medical applications. Laser power is the most significant factor for micro-hardening and wear resistance. Rank two for scanning speed and three for standoff distance, respectively. The experiments show that the surface micro-hardness of treated samples varies from 711 to 833 Vickers Pyramid Number by optimized process parameters such as laser beam power of 300 W, laser scan speed of 1.0 mm/s, and standoff distance of 225 mm. In comparison, the base material micro-hardness is 208 Vickers Pyramid Number as the predictive equation generated for finding micro-hardness value for the above three laser hardening process parameters. The dry sliding wear test is conducted on all laser-treated samples and a comparison is made with the untreated sample. A significant improvement in wear resistance was observed for treated as compared to untreated samples. The wear of laser hardened sample of SAE 420 steel was 3.67 x10-9 g/cm compared to untreated base metal wear rate of 139.00 x 10-9 g/cm at an applied load of 30 N and sliding speed of 300 revolutions per minute. The scanning electron microscopy analysis of wear samples (untreated, treated maximum, and minimum hardness) is observed for investigating material removal patterns.

Optimization of technological parameters at discrete strengthening of steel cylindrical surfaces

The technologies of continuous strengthening of technological surfaces have practically exhausted their capabilities, which calls for the creation of fundamentally new approaches. The application of the principles of discrete-oriented strengthening of tribosystems has wide prospects for improving existing methods of strengthening due to the selection of modes and control of the geometric structure of the surface layer. The essence of the discrete-oriented strengthening method is the application of combined electromechanical processing and electrocontact cementation of cylindrical surfaces. The purpose of the work is to determine the parameters of discrete processing of cylindrical steel parts that are optimal according to the surface hardness criterion. Using the Statistica program, a factorial experiment was implemented according to the Box-Behnken plan, and the results of dispersion and regression analysis of the influence of processing parameters on microhardness were obtained. It was established that the following optimal parameters of DOZ processing are necessary to achieve the maximum values of microhardness (5950 MPa): current strength-500A, force-350 N, contact time-0.3 s.

Study of Wear Resistance of Cylindrical Parts by Electromechanical Surface Hardening

The work scientifically substantiates the use of an effective technology for increasing the wear resistance of cylindrical parts, using the example of protective sleeves of cantilever pumps, due to electromechanical surface hardening. A review of research was carried out and it was established that the achievement of the highest values of microhardness of the surface layer at a depth of up to 1.2 mm is possible during electromechanical processing of protective sleeves of cantilever pumps. The application of various modes and schemes of electromechanical surface hardening (EMSH) is accompanied by a change in structure and, as a result, an increase in the hardness of the surface layer of the bushings. The actual contact area of the tool roller with the processed surface and the depth of the temperature-deformation effect depend on the physical and mechanical properties of the materials and the pressing force. The formation of a temperature gradient in the hardened zone at a depth of up to 1.2 mm from the surface has been proven. Metallographic analysis of the surfaces of the sleeves treated by EMSH shows the formation of a white layer with reduced etchability and increased hardness in the hardening zones. The results of the X-ray structural analysis confirmed the formation of the martensite phase in the hardening zone. The microhardness of the hardened steel zone increased by 2.6...3.6 times compared to the initial values at a depth of up to 1 mm from the surface, depending on the materials. In the case of their overlap, the alternation of a fully hardened zone, a partially hardened zone, and a self-relief zone is observed. At the same time, the microhardness of steels along the surface depends on the hardening scheme.&#x0D; Wear tests under friction conditions of parts of cantilever pumps paired with stuffing boxes showed that the wear resistance of protective sleeves after EMSH increased by 3.1 times for 45 steel, 1.9 times for U8 steel, 2.5 times for SHKH15 steel, for cast iron by 1.9 times compared to the initial values. The use of U8 steel samples after EMSH, instead of serial bushings made of steel 45, allows to increase the wear resistance of parts by 6.1 times, which allows us to recommend U8 steel for use in the manufacture of protective bushings for console pumps. On the basis of the research, recommendations are given for the application of EMSH for the formation of a surface layer with increased wear resistance of protective sleeves during their production and during repair of console pumps in workshops or service centers of agribusiness companies.

Influence of Duty Cycle on the Phosphorus Content and Hardness of the Ni-P Coatings Produced by Pulse-Current Electroplating

Ni-P coatings were prepared on low carbon steel substrates using the pulse electrodeposition method. The influence of the pulse duty cycle on the phosphorus content and hardness of the Ni-P coatings was investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to examine the surface morphology and chemical composition of the Ni-P coating layers. The results showed that an increased pulse duty cycle (20% - 80%) led to a decreased phosphorus content from 17.81 wt.% to 13.71 wt.%. The microhardness values were found to have an inverse relationship with the phosphorus content. The highest hardness of 538.22 ± 12.92 HV0.1 was obtained from the sample produced with a duty cycle of 80%, which had the lowest P content of 13.71 wt.%.

Scratch resistance and in-vitro biocompatibility of plasma-sprayed baghdadite coatings reinforced with carbon nanotubes

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) coatings, commonly used for metallic implants, have limitations such as excessive brittleness, low fracture toughness, inadequate wear resistance, and slow osseointegration properties. In contrast, baghdadite (BAG, Ca3ZrSi2O9), a calcium zirconium silicate-based bioceramic, exhibits outstanding biological properties, to promote cell proliferation and differentiation of human osteoblasts along with adequate mechanical strength. In this study, plasma-sprayed HA, BAG, and carbon nanotubes (CNT, 1 wt%, and 2 wt%) reinforced BAG coatings are deposited on titanium (Ti) substrate to enhance its mechanical as well as biological properties. The microhardness values of CNT-reinforced BAG coatings increase due to a decrease in porosity and the retention of CNT inside the BAG matrix. Progressive loading scratch tests are performed, revealing a reduction in wear volume loss from 15.051 mm3 to 12.574 mm3 and scratch rate from 43.262 mm3N−1 m−1 to 36.172 mm3N−1 m−1 with the addition of 2 wt% CNT in BAG coatings. The scratch hardness test results demonstrated that introducing CNT into BAG coating significantly enhances its performance, showing a remarkable 38.7 % improvement. In-vitro cell culture studies indicate excellent cell adhesion, growth, and proliferation of MC3T3-E1 osteoblast cells on the surfaces of the CNT-reinforced BAG coatings.

Effect of high-pressure torsion on the structure and microhardness of biodegradable Fe-30Mn-5Si (WT.%) alloy

The effect of high-pressure torsion (HPT), including a new method of accumulative HPT (AccHPT), on the microstructure and mechanical properties of Fe-30Mn-5Si alloy is studied. It is shown that during HPT and AccHPT, stress-induced ε-martensite is predominantly formed, and a mixture of nanograined structure, nanosubgrained structure and highly-dislocated substructure after HPT, while predominantly nanograined structure after AccHPT, are obtained. The increase in the number of HPT revolutions results in a broadening of the X-ray diffraction lines and higher microhardness values. The highest values were achieved on samples after AccHPT.

Experimental study of SS316L, Inconel 625, and SS316L-IN625 functionally graded material produced by direct laser metal deposition process

Three types of walls were produced by the direct laser metal deposition (DLMD) process; SS316L, Inconel 625 (IN625), and SS316L-Inconel 625 FGM. The thin walls were deposited on an AISI 4130 austenitic steel substrate in five layers with a length of 2 cm. The solidification behavior, secondary dendrite arm spacing (SADS) value, chemical composition, and hardness of samples were studied. Microstructures were evaluated using optical microscopy (OM) images, scanning electron microscopy (SEM), EDS Line, EDAX, and Map analyses. OM and SEM images showed an acceptable bonding between the layers in all samples. The main solidification was equiaxed dendritic and columnar dendritic in most parts. The growth of dendrites was perpendicular to the substrate. Some dendrites grew epitaxially at the interface of two sequential layers. The standard deviation of SDAS value for SS316L, IN625, and SS316L-IN625 FGM was 0.63, 0.71, and 0.73, respectively. The lowest value of SDAS was obtained in layer one, while the highest value was obtained in layer five of the thin walls. The average SDAS values for SS316L, IN625, and SS316L-IN625 FGM were 4.40, 4.53, and 4.76 µm, respectively. Therefore, the difference between the SDAS values was not significant. EDAX and Map analyses showed that the segregation of Nb and Mo to the dendritic boundary and the formation of eutectic, secondary phases, and brittle Laves phases have occurred. Additionally, the segregation of Nb and Mo to the dendritic boundary in the SS316L-IN625 FGM sample was higher than SS316L and IN625 samples. The microhardness values oscillated significantly and decreased by moving away from the substrate (in the build direction). The microhardness values of different points of the SS316L-IN625 FGM walls were in the range of 218–278 HV. EDS line scan, microstructure, and microhardness analyses indicated the successful fabrication of the SS316L-IN625 FGM by the DLMD process.

Hydroabrasive wear of jet pump nozzles

The measurements of hydroabrasive wear of the jet pumps nozzles, used on dredges operating on transferring pulp, are carried out. The measurement result is compared with the result of modelling the flow in the pump suction chamber near the nozzles. The modelling is carried out using the Fluent program complex as a part of the Ansys program; the pure water is being modelled in the suction pipe. This assumption is made taking into account that pulp contains approximately 10 percent by volume of sand, therefore the trajectories of sand particles movement coincide with the streamlines of water. The results of modeling have shown, that the angle of attack on the surface of nozzle nose part nearest to the pulpline outlet is close to zero, whereas the angles of attack on the surface of the nozzle nose part furthest from the pipeline outlet differ considerably from the zero and range from 20 to 50 degrees, that is the values at which the hydroabrasive wear increases severalfold compared to the angles close to zero. The results of modelling are confirmed by the examination of the worn nozzles. It is turned out that the nose part of the nozzles wears out along a circle unevenly, the part furthest from the pipeline outlet wears at higher rate, that leads to the bevel of the plane of the nozzle nose opening, the bevel angle reaches 20–25 degrees. The microhardness values of the nose part of the worn nozzle are also in agreement with the results of modelling. The measurements have shown, that the microhardness of the nose part of the worn nozzle is uneven along a circle, and the microhardness of the most worn side of the nozzle nose is least. This fact indicates that the different zones of the surface of the nozzle nose part differ from each other by the rigidity of stress state scheme in hydroabrasive attack. It can be used later in choosing the regime of laboratory tests on hydroabrasive wear.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ДОБАВКИ ВЫСОКОДИСПЕРСНОЙ ФАЗЫ КАРБИДА ТИТАНА, СИНТЕЗИРОВАННОЙ В РАСПЛАВЕ, И ТЕРМООБРАБОТКИ НА СТРУКТУРУ И СВОЙСТВА СПЛАВА АМ4,5Кд

The study results are given which are devoted to finding the effect of reinforcement with fine phase of titanium carbide in the amount of 10 masses% on the physico-mechanical and tribotechnical properties of industrial aluminum AM4.5Kd alloy. The physico-mechanical (density, porosity, coefficient of thermal linear expansion, hardness, microhardness) and tribotechnical (wear rate, friction factor, self-heating temperature) properties of the composite material AM4.5Kd-10%TiC obtained by self-propagating high-temperature synthesis before and after heat treatment are analyzed. It is found out that composite samples after heat treatment have a good combination of physical and mechanical properties, namely a low level of porosity, a low value of the coefficient of thermal linear expansion, and the values of hardness and microhardness are increased twice. Special attention should be paid to the fact that reinforcement with a ceramic phase in combination with heat treatment leads to a significant increase in the level of wear resistance of the matrix alloy (by 9 times) and a decrease in the friction factor (by 4 times). Thus, according to the results of the studies conducted, the resulting composite material AM4.5Kd-10%TiC can be recommended as a material used in tribological assemblies.