Microstructure and Mechanical Properties of TiC/TiB Composite Ceramic Coatings In-Situ Synthesized by Ultrasonic Vibration-Assisted Laser Cladding

Laser cladding coating has many advantages in surface modification, such as a small heat-affected zone, and good metallurgical bonding. However, some serious problems such as pores, and poor forming quality still exist in the coating. To suppress these problems, a novel process of ultrasonic vibration-assisted laser cladding process was adopted to in-situ synthesize TiC/TiB composite ceramic coating on the surface of titanium alloy. Results showed that the introduction of ultrasonic vibration effectively improved the surface topography of the coating, reduced the number of pores in the coating, refined the crystal grains of the coating, decreased the residual tensile stress in the coating, and increased the micro-hardness of the coating. The tribological properties of the coating were significantly improved by the ultrasonic vibration, the wear resistance of the coating fabricated with ultrasonic vibration at power of 400 W increased about 1.2 times compared with the coating fabricated without ultrasonic vibration, and the friction coefficient decreased by 50%.

Process Simulation and Abrasion Behavior of Jet Electrodeposited Ni–TiN Nanocoatings

In this work, we study jet-electrodeposited Ni–TiN composite nanocoatings (CNCs) for improving abrasion resistance as a function of various nozzle diameters. In addition, COMSOL software is utilized to simulate the process of jet electrodeposition, particularly the influence of spraying speed and pressure of the electrolyte on the abrasion resistance of coatings. Optimization of the nozzle diameter to obtain uniform and high-performance coatings showed that a Φ7 mm nozzle diameter generated the optimum spraying speed and spraying pressure, which results in good micro-hardness and abrasion resistance of the Ni–TiN CNCs. Under these conditions, the 45 steel substrates are coated with a compact layer of uniform and nano-sized TiN particles, which are responsible for the high abrasion resistance of our Ni–TiN CNCs. Our study may motivate researchers to study jet electrodeposition in order to obtain abrasion-resistant coatings.

MIG and TIG Joining of AA1070 Aluminium Sheets with Different Surface Preparations

In this work, AA1070 aluminium alloy sheets are joined using TIG and MIG welding after three different edge preparations. Shearing, water jet and plasma-cut processes were used to cut sheets, subsequently welded using ER5356 and ER4043 filler metals for TIG and MIG, respectively. Mechanical properties of the obtained sheets were assessed through tensile tests obtaining a relation between sheet preparation and welding tightness. Micro-hardness measures were performed to evaluate the effects of both welding and cutting processes on the micro-hardness of the alloy, highlighting that TIG welding gives rise to inhomogeneous micro-hardness behaviour. After tensile tests, surface fractures were observed employing scanning electron microscopy to highlight the relation between tensile properties and edge preparations. Fractures show severe oxidation in the water jet cut specimens, ductile fractures and gas porosities.

Influence of Different Dielectrics on Process Performance for Electrical Discharge-Assisted Milling of Titanium Alloy

Electrical discharge-assisted milling (EDAM) is an effective method for machining titanium alloys according to previous research. In this study, the influence of three different dielectrics (kerosene, EDM oil, and deionized water) on the EDAM performance was studied. Experimental studies reveal the influence of different dielectrics by analyzing the discharged signal, surface morphology, and elemental composition of the electrode. The results show that kerosene and EDM oil have a higher discharge frequency than deionized water. After a long discharge time, carbides and debris were generated during the machining process, which affected the micro-hardness and the discharge stability of the machined material. In EDAM, EDM oil can produce the best surface quality, and the surface roughness value was 34.93%, 87.92%, and 121.68% higher than that of kerosene, deionized water, and conventional milling (CM), respectively.

Forming of Composite Cutting Layer on Tool Steel by Heat Treatment of CVD Coatings

СVD chromium coatings are evaporated on steel substrate from chrome-organic compounds. For crystallization with forming of nano-particles of chromium carbides, subsequent heating (annealing) of tool steel with hybrid coatings is carrying out. Significant increase of micro-hardness of the coating up to 27000 MPa is observed due to the dispersion strengthening. Optimal annealing parameters (temperature and duration) are determined, which maximally strengthen the coatings and increase their adhesion to the steel substrate.

Comparison of the Effects of Sugar-free Solutions, Cola, Mouthwash on the Surface Hardness and Roughness of Temporary Crown Materials

The aim of this study is to investigate the effect of polishing with different solutions on the surface roughness and hardness of two different polymethylmethacrylate temporary restoration materials. In the study, two different temporary crown materials prepared in the CAD / CAM system and prepared by the traditional method were used to test a total of 224 pieces of 10 mm diameter and 2 mm thickness. After the surface roughness and micro hardness values were measured, samples were randomly divided into seven groups among themselves; After waiting 24 h, 1 and 3 weeks, values were measured again. Data were evaluated using 3-way analysis of variance (ANOVA) and Tukey HSD test. The temporary restorative materials surface hardness and roughnesses are important to be able to stay in oral cavity without any changes. And it is also important to determine which of the materials (prepared by temporary conventional materiels or by the CAD/CAM) are less effected by the liquids in oral cavity.

Slippage during high-pressure torsion of commercially pure titanium and application of accumulative HPT to it

A new efficient method was used to find that in the case of high-pressure torsion of commercially pure titanium, accumulation of shear strain in Ti does not occur due to slippage of anvils. Despite this, micro-hardness increases as the number of turns n increases, and Ti structure is refined more intensively. High-pressure torsion is accompanied by a high-pressure ω-phase formation. However, the content of ω-phase changes non-monotonously with an increase in the number of turns. First, while number of turns is less than n=5, the ω-phase content reaches 50%. Upon further deformation, the ω-phase content decreases to 15% for n=20. A new accumulative high-pressure torsion method is applied to commercially pure titanium for the first time. Accumulative high-pressure torsion leads to the strongest transformation of the structure and an increase in hardness, since stronger real deformation occurs due to composition of compression and torsion strain cycles.

Physico-chemical properties of irradiated poly (vinyl alcohol)–Ethylene glycol blend films by γ-rays and ion beam

Poly (vinyl alcohol) is blended with ethylene glycol by casting method to form PVA-EG blend films. These films were irradiated by both N2 ion beam extracted from dc ion source at different ion fluences and γ-rays with various irradiation doses. The effects of ion beam and γ-rays irradiation on the thermal, micro-hardness, and gel fraction properties of PVA-EG blend films were investigated. The gel fraction % and micro-hardness increase with increasing the γ-rays doses up to 150 kGy and then decreased, where they increased at all fluences of ion beam irradiation. The improvement in the gel fraction percentage and micro-hardness suggest that PVA-EG blend films exhibited a crosslink density. The thermal behavior was examined by thermogravimetric analysis and it shows different thermal patterns depending on the type and dose of radiation. The thermal stability parameters of γ-rays- and ion beam-irradiated PVA-EG samples were evaluated using the Ti, Ts, T0.5, Tf temperatures, and activation energy (Ea) values. The thermal stability parameters were dependent on both the type and extent of irradiation dose and fluence. Finally, there is a good agreement between the obtained results from different measurement techniques.

Characterization and Corrosion Resistance Behavior of Pure Ni Coatings & Ni-V2O5 Nano composite Coatings Developed by DC & PC Methods of Electrodeposition

Pure nickel (Ni) coating and nickel – vanadium pentoxide (Ni-V2O5) nanocomposite coatings have been developed on mild steel substrates by direct current (DC) & pulse current (PC) methods of electrodeposition using sulfamate electrolyte bath by optimizing all the suitable parameters. The surface morphology and texture characterization of pure Ni coating and Ni-V2O5nanocomposite coatings were analyzed by spectroscopic techniques such as Scanning Electron Microscopy (SEM) equipped with an attachment for Energy Dispersive Spectrometry (EDS) & X-ray Diffraction (XRD) spectroscopy analysis. The SEM study confirmed surface morphology of the pure Ni coating was changed by the incorporation of V2O5 nanoparticles in the nickel metal matrix and chemical composition of all the coatings was determined by EDS. XRD study proved highly corrosion resistant nanocomposites show preferred orientation towards (111) plane. The corrosion rate of all the coatings was investigated in 3.5% corrosive medium using electrochemical techniques such as Tafel extrapolation and AC impedance. The coatings developed by PC show enhanced corrosion resistance behavior compare to coatings developed by DC. The 0.125g/L Ni-V2O5nanocomposite coating obtained by PC show more widened semicircle with high Rp value and has more positive shift with high corrosion resistance during AC impedance and Tafel extrapolation analysis respectively. The coatings developed by PC showed improved micro hardness compare to coatings developed by DC during micro hardness testing of all the coatings.