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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 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.

Nickel-based superalloys are used widely in the critical areas of applications such as aerospace, marine, power and many process industries. In this study, solid particle erosion behavior of cast nickel-based CY5SnBiM was analyzed at room temperature. The velocity and angle of the study were set to 59 m/s, 92 m/s and 124.137 m/s, and 30°, 45°, 60° and 90°, respectively; this resembles the exact industrial valve applications. Macrographs were taken to identify the wear scar of material at different angles and different velocities. X-ray diffraction (XRD) was carried out on the material to observe the nature of precipitates. Scanning electron microscopy (SEM) was carried out to identify the plowing action on the material by the erodent in the case of lower angle due to ductile nature of the material. In the case of higher angle, it develops deep pits and craters due to rebounding of erodent particles.

Aluminium composite with VAL12 as matrix and La2O3 as dispersoids fabricated through liquid metallurgy route involving liquid forging operation through squeeze casting process in the present investigation. The frictional characteristics of as-cast aluminium composites are studied under dry sliding wear tests by varying the service factors. The samples prepared were examined for its uniform distribution of the reinforcement, phases formed using advanced characterization facilities. Taguchi orthogonal array method is employed in designing the experiments, and the responses are recorded in terms of wear rate and frictional coefficient. The mechanistic studies are carried out by analyzing the wear surface morphology using SEM. Predominantly AMMC shows delamination and abrasion at higher loads due to thermal softening and adhesive mechanisms at lower loads. Load and sliding distance majorly characterize the wear behavior of the AMMCs under un-lubricated sliding conditions.

Duplex stainless steel (DSS) is having an equal fraction of ferrite and austenite. Chromium, Nickel, Molybdenum, and few minor alloying elements constitute a DSS system, which makes metallurgy of the system complex. Proper heat treatment is need of the hour when it comes to expecting desired properties from the material, subjected to a specific working environment. DSS is one of the favourite choices for oil and gas industries. This study focuses on optimizing the heat treatment parameters and heat treating the as-cast 5A DSS and investigating microstructural evolution of the material subjected to various quenchants such as brine, water, and polyethylene glycol. Heat treatment temperatures, quenching media, and the quenching time have been selected in accordance with ASTM standards. Thermocalc TCFE8 database is being used for understanding the material response to various heat treating temperatures.

Niobium addition to base alloy significantly reduces the formation of deleterious phases, in particular, sigma phase when the material is sensitized at 900 °C. In this paper, hyper-duplex stainless steel with 0.47% of Niobium (Nb + CD3MWN - 7A) was casted using induction melting furnace and then heat-treated under two different heat treatment temperatures of 1160 °C and 900 °C to explore the properties such as microstructure and hardness for further study. The erosion test was carried out in air-jet erosion tester at room temperature with different erodent velocities. The study was done with a constant impact angle of 45°. Microstructure analysis was carried on two different heat-treated samples as well as on eroded samples using scanning electron microscope coupled with energy-dispersive analysis spectroscopy to confirm the presence Niobium carbide precipitation in sensitized sample at grain boundaries. Erosion test results showed that erosion rate is lower in sensitized sample when compared to solutionized sample because of their higher hardness in sensitized sample.

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.