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The effect of microstructure of nickel-aluminum bronze alloy (NAB) on the corrosion behavior in artificial seawater is studied using linear polarization, impedance and electrochemical noise tests. The alloy was heat treated in different heating cycles including quenching, normalizing and annealing. Microstructure of the specimens was characterized...
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Citations
... It is reported that increasing the nickel content is enhanced the corrosion resistance of these alloys [5,6]. Besides, the microstructure of these alloys can be controlled by modifying their surfaces and subsequent heat treatment, where the volume fraction and the distribution of the constituent phases depend on the temperature and cooling rate [3,7,8]. The forceful wear resistance of the aluminum-bronze makes it the excellent selection for heavy-duty sleeve bearings and machine tools [5]. ...
This study investigated the effect of ferrite band formation for preventing the diffusion of molten copper (Cu) into steel grain boundaries. To this end, the gas tungsten arc welding method was exploited for cladding ERCuAl-A2 and ERCuSi-A filler metals on plain carbon steel. Then, microstructure, cracks, and ferrite bands were characterized and the conditions for the formation of 4.20 wt.% Si in the ferrite band were evaluated using the design of experiments methodology. The results indicated that when cladding with 7.60 wt.% Si takes place with minimum heat input (0.9 kJ/mm), the penetration of the molten Cu will not occur in the grain boundaries of the heat-affected zone in the presence of the %overlap.
... Considerable methods have been investigated to improve the corrosion resistance of as-cast NAB alloy. Heat treatment was adopted to homogenize the microstructure by reducing the preferential corroded β' phase [12], but it can only eliminate β' phase partly, and the inherent susceptibility to selective phase corrosion was still inevitable. Frictionstir processing reduced static immersion corrosion rate for the refined the microstructure [13][14][15]. ...
As-cast nickel-aluminum bronze is prone to suffering selective phase corrosion in marine environments. To solve this problem, chromium was introduced via ion implantation to modify its surface microstructure, which was characterized by high-resolution transmission electron microscopy and auger electron spectroscopy. The corrosion behavior was studied by electrochemical measurements and salt spray test. It was found that the inherent selective phase corrosion in as-cast NAB was inhibited effectively when the implantation fluence was 5 × 10¹⁷ ions/cm². The improved corrosion resistance after ion implantation was believed to stem from the rapid formation of a more protective film containing chromium oxides and hydroxides.
... It has been reported that the rate of crevice corrosion of the alloy in seawater is about 0.7 -1.0 mm y-1 [7,8]. The optimum mix of tested mechanical proper-ties with ultimate tensile strength in the range of 325 MPa, elongation of around 60% and Rockwell hardness values of 46.5 -63.7 HRc, making this alloy suitable as alternatives to steel in low/medium strength structural applications [9]. ...
The influences of Ce, Sm and Yb on cavitation erosion of NAB alloy in 3.5% NaCl solution are evaluated using mass loss, SEM, 3D morphology and Tafel plot, respectively. The results show that the addition of Ce or Sm or Yb enhances the mechanical property of NAB alloy, and the sizes of κⅠ and κⅡ phases within NAB alloy decrease with adding Ce or Sm or Yb, resulting in the prevention of the propagation of the cracks caused by cavitation erosion initially originated at the phase boundaries between α and κ phases, and finally the cavitation erosion damage significantly decreases with adding Ce or Sm or Yb. The corrosion of NAB alloy in 3.5% NaCl solution can promote the cavitation erosion of NAB alloy, while the corrosion resistance of NAB alloy increases with the addition of Ce or Sm or Yb, and then the cavitation erosion resistance is accordingly improved with the addition of rare earth element.
Due to increase in demand to enhance the operating characteristics of materials and at the same time to reduce their overall mass, there is a need to produce the surface layers with the required characteristics so as to increase their functional properties. For the last many years, numerous methods have been used to produce the surface layers. Friction Stir Processing, a method developed recently, is primarily used for the modification of material’s microstructure on the surface layers. In this study, surface composites by Friction Stir Processing for the marine applications have been discussed.
In this research, the effect of annealing and age hardening treatment on mechanical properties of cast nickel aluminum bronze (NAB) C95800 was assessed through Vickers hardness, tensile and bending fatigue and the influence of heat treatment has been elucidated. The results showed that heat treatment cycles by changing the microstructure alter the mechanical properties of the alloy. Between annealing and age hardening, ageing process improved hardness, tensile strength and fatigue strength by 40%, 20 and 60%, respectively. The as-cast and aged specimens displayed the least and the highest strength in tensile and fatigue tests, respectively.
In this research, the effect of annealing and age hardening treatment on mechanical properties of cast nickel aluminum bronze (NAB) C95800 was assessed through Vickers hardness, tensile and bending fatigue and the influence of heat treatment has been elucidated. The results showed that heat treatment cycles by changing the microstructure alter the mechanical properties of the alloy. Between annealing and age hardening, ageing process improved hardness, tensile strength and fatigue strength by 40%, 20 and 60%, respectively. The as-cast and aged specimens displayed the least and the highest strength in tensile and fatigue tests, respectively.
Nickel Aluminum Bronze (NAB) alloy specimens subjected to Friction Stir Processing (FSP) with and without particulate addition were subjected to tribological testing in a reciprocating sliding tester which can perform sliding test on specimens immersed in sea-water. Stainless steel ball was slid against flat coupons of NAB as cast, and Friction-Stir-Processed NABs, under sea-water to study the wear performance considering their prospective use in marine bearing applications. The wear expressed in terms of the wear scar area measured using an image processing method indicates that the performance of the Friction-Stir-Processed NABs in sea-water environment is inferior to that of the un-processed NAB, even though the processed NABs have relatively superior hardness. While wear tests in dry condition indicate that the wear resistance for the friction stir processed samples is high, under saline environment the trend was found to be reversed, as their wear resistance was found to be low. The reduction in wear resistance in sea-water is explained in terms of the (electrochemical) corrosive wear mode being active in the saline medium. The surface damage as revealed from the SEM characterization of wear scars were found to correlate with the experimental deductions.
Cavitation erosion-corrosion of nickel aluminium bronze with oxide films formed under two different conditions, oxide formed in air for 1 week and oxide formed after 3 months immersion in 3.5% NaCl solution, was conducted using a 19.5 kHz indirect ultrasonic vibratory system at a peak-to-peak amplitude of 80 (±0.2) μm in 3.5% NaCl solution. The synergistic interactions between the cavitation erosion and corrosion were determined via experiment comprising of three different tests: pure cavitation erosion test in distilled water, pure in-situ electrochemical corrosion tests using open circuit potentials (OCP) and polarization scanning, and a combination of cavitation erosion-corrosion kept at OCP in 3.5% NaCl solution to understand the overall synergism existing between cavitation wear and corrosion. The results were then analysed and compared using mass loss analysis. Scanning electron microscopy was used to analyse microstructural characteristics of the cavitated sample surfaces, as well as the transverse-sections of the surface features. It was seen that samples with water formed film exhibited high synergy and was more susceptible to selective phase attack and phase boundary erosion in comparison to air-formed film.
