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Austenitic-ferritic steel, as suggested by its name, has an equal fraction of austenite and ferrite phases, also known as duplex stainless steels (DSS), are one of the highly used materials for subsea pipelines applications. The presence of slurries is inevitable in subsea pipelines. This technical work elucidates the slurry erosive wear behavior of duplex stainless steel and the impact of the addition of niobium (Nb) on the phenomena. Vacuum induction melting was used to produce duplex stainless steel, and its Nb added casts. The aim of the work is to compare both castings' for erosive wear behavior using a slurry jet erosion tester. Computational thermodynamic software Thermo-calc was used to investigate the presence of numerous phases in the system. X-ray diffraction (XRD) has confirmed the formation of niobium carbide in the steel, indicated by Thermo-calc. The effect of slurry velocity (30, 40, and 50 m/s) and impingement angle of slurry (30°, 45°, and 90°) on wear characteristics of these castings were analyzed using volume loss measurements, optical profilometry, and scanning electron microscopy (SEM). The erosion rate of both the materials increased with increasing velocity, whereas erosion was more at shallow angles of impact and increased significantly at the slurry jet's normal incidence. Refinement of austenitic grains in the ferritic pool hints at an increase in heterogeneous nucleation in Nb-doped samples; at the same time, the samples have shown increased hardness and superior erosion resistance against the slurry jet impact.

The aim of this paper is to investigate the mechanical properties of Nickel Aluminium Bronze (NAB) alloying with Niobium (Nb) and Yttrium (Y) rare earth metals. NAB alloy frequently used in the aqueous solution as well as less widely used deployed materials were studied. To avoid failures due to aqueous environment. Niobium (Nb) and Yttrium as chosen alloying addition with NAB. The Nb and Y rare earth element which acts as stabilizing element to existing NAB system to optimize the mechanical properties. The NAB with alloying elements processed in the vacuum induction furnace by means of predetermined parameters. After casting, the samples were tested for the mechanical properties like tensile and Brinell hardness to ensure improvements with the master NAB system. At the same time, the characterization techniques SEM and EDAX with mapping analysis confirmed the chemical proportions of the elements in the developed NAB with proposed NAB (Nb) and NAB (Y) alloys. A comparative study is to be made for the NAB with Nb and Y under aqueous environment based for the developed alloys.

An investigation was carried in Nickel Aluminium Bronze (NAB) alloyed with Niobium (Nb) and Yttrium (Y) to study the effect of the microstructure for onshore applications. Nickel Aluminium Bronze is broadly used in aqueous atmospheres due to their good mechanical and corrosion resistance properties. The presence of destructive species in aqueous water initiates the corrosion of the engineering modules is inevitable. In-order to optimize the corrosion resistance Nb and Y were added as (1%, 2% & 3%) respectively in the master NAB. The specimens were exposed to the immersion test in NaCl solution. To create the behavior of corrosion and succeeding erosion, altered immersions hours were selected as 8, 16, 24, 32, 40, 48 and 54 h. The mass loss measurements were obtained after the completion of the individual specified time to calculate corrosion rates (CR). Solid particle erosion (SPE) investigations were also carried out on the developed alloys. The size of the particle which is used in the investigation is 50 µm. Corrosion rate was calculated and it is correlated with the immersion time. Scanning electron microscopy (SEM) investigations were observed for the corroded and eroded specimens.

Duplex stainless steels (DSS) exhibit excellent corrosion resistance and mechanical properties to the severe environments and hence are used in many engineering applications such as oil and marine industries, chemical storage, nuclear power plants, and many more. These are used as valves, fittings, and pipes to suck the crude oil in oil fields. Austenite (γ) and ferrite (δ) phases constitute the microstructure of DSS. However, one needs to control both the phases towards making it lucrative in desired applications. Investigations on tribological behavior of cast DSS are limited. The current work focuses on optimizing the wear parameters for slurry jet erosion and analyzing their effect on wear of the 5A DSS. Grey relation analysis (GRA) and Taguchi design of experiments have been used for optimization. Slurry jet erosion tester was used investigate the response of the material to various designed experiments. Worn-out surfaces morphologies and wear mechanisms were revealed using Scanning electron microscopy (SEM), whereas white light interferometer was used to understand 3D morphologies the surfaces.

Nanocrystalline powders of 4 mol.% GdO1.5-4 mol.% SmO1.5 doped ZrO2 (4Gd4SmSZ) has been synthesized by co-precipitation process. Their phase transformation and crystalline growth behavior was investigated by Thermo gravimetric-Differential Thermal Analysis (TG-DTA), X-ray Diffraction (XRD), Raman spectroscopy and High-Resolution Transmission Electron Microscopy (HR-TEM) after calcinations at different temperatures. The XRD, Raman spectra and HRTEM results confirm the nature of tetragonal zirconia (t-ZrO2). The prepared 4Gd4SmSZ powders, remains in the single metastable tetragonal phase over the whole calcination temperature ranging from 873 K to 1273 K for 2 h. The crystallite size varies from 11.98 nm to 18.90 nm with increase of temperature from 873 K to 1273 K. The activation energy of the prepared powders at low temperature is considerably lesser than that at a higher temperature. The annealed 4Gd4SmSZ powders had shown excellent phase stability at 1573 K for 100 h. Keywords: Zirconia, Coprecipitation, Rare earth oxide, Phase transformation, Tetragonal, Activation energy

The effect of cerium addition on AZ91 magnesium alloy and its influence on stress corrosion cracking (SCC) were studied using constant load proof ring testing NaCl-K2CrO4 and ASTM D1384 solutions at 70 and 80% of yield stress, respectively. The investigation revealed that the optimum grain refinement of desired phases occurred with 0.5% addition of cerium. The addition levels of cerium above 1.5 wt.% to AZ91 alloy resulted in premature failures due to poor SCC resistance in both solutions (K2CrO4 and ASTM D1384 solutions). The microstructural studies of the experimental alloys were characterized by using optical and scanning electron microscopy. The elemental compositions of cerium-added AZ91 magnesium alloys were studied by energy-dispersive spectroscopy. The results indicate that the mode of SCC failure was found to be transgranular in nature along with secondary cracks containing cleavages which resulted from the hydrogen embrittlement and anodic dissolution phenomena. The AZ91 alloy with 0.5 wt.% cerium exhibits better mechanical properties and high stress corrosion resistance.

In this work multi-component equiatomic and non-equiatomic AlCoCrCuFeTix hexanary high-entropy alloys (HEA) was synthesised through mechanical alloying. The prepared powder was sintered via spark p...

Nanocrystalline samaria (8 mol%) doped zirconium oxide (8SmSZ) was synthesized using reverse co-precipitation technique, the calcination temperature ranging from 873 K to 1273 K for 2 h. XRD structural analysis results confirm the tetragonal(t) nature of the synthesized 8SmSZ nanocrystalline powder. The calculated crystallite size of tetragonal zirconia calcined at 873 K is around 9.0±0.5 nm and with increase in calcination temperature the size increases to 16.0±0.8 nm (1273 K). Thermogravimetric-Differential thermal analysis (TG-DTA) was carried out to study the crystallisation kinetics and growth behaviour of the 8SmSZ. The activation energy for the crystallisation of tetragonal ZrO2 formation in the 8SmSZ powder was found to be 308.1 kJ/mol by a non-isothermal DTA method. The growth morphology parameter was found to be n=2 indicating two-dimensional growth. The phase stability of the samples after annealing at 1573 K for 100 h was investigated by Raman spectroscopy and it was found that samaria doped zirconia exhibits better phase stability. These preliminary results confirmed the higher phase stability at elevated temperature thereby confirming its suitability in thermal barrier coating (TBC) applications.

Nanocrystalline powders of ZrO2–8mol%SmO1.5 (8SmSZ), ZrO2–8mol%GdO1.5 (8GdSZ), and ZrO2–8mol%YO1.5 (8YSZ) were prepared by a simple reverse-coprecipitation technique. Differential thermal analysis/thermogravimetry (DTA/TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were used to study the phase transformation and crystal growth behavior. The DTA results showed that the ZrO2 freeze-dried precipitates crystallized at 529, 465, and 467°C in the case of 8SmSZ, 8GdSZ, and 8YSZ, respectively. The XRD and Raman results confirmed the presence of tetragonal ZrO2 when the dried precipitates were calcined in the temperature range from 600 to 1000°C for 2 h. The crystallite size increased with increasing calcination temperature. The activation energies were calculated as 12.39, 12.45, and 16.59 kJ/mol for 8SmSZ, 8GdSZ, and 8YSZ respectively.

Equi-atomic and non equi-atomic multi-component systems were synthesized through different routes to form high-entropy single solid solution. One such high-entropy alloy (HEA) with hexanary composition AlCoCrCuFeZn x was synthesized using mechanical alloying. The effect of zinc variation on the crystal structure and phase formation was characterized using XRD, FESEM with EDS and TEM. The synthesis resulted in both equi-atomic and non equi-atomic nano crystalline AlCoCrCuFeZn with a crystallite size less than 10 nm.