R. Ahmad

Improvement in the pitting resistance of Inconel-600 by nitrogen ions implantation

The surface of Ni-Cr-Fe (Inconel-600) alloy was modified by implanting 500 keV nitrogen ions at room temperature using pelletron accelerator to dose of 1.87 × 1014 ions/cm2. X-ray diffraction analysis of the ions implanted samples indicated the formation of Cr2N phase. Electrochemical testing of Inconel-600 alloy before and after the ions implantation was conducted using potentiodynamic tafel scan, potentiodynamic anodic polarization and electrochemical impedance spectroscopy techniques in an acidic saline solution. The higher anodic polarization slope (βa), low cathodic polarization slope (βc) and decrease in corrosion current density after ions implantation were attributed to the modification of passive film by the nitrogen ions. The scanning electron microscopy and electrochemical analyses of the ions implanted samples revealed an improvement in the pitting resistance of the alloy.

Annealing and Test Temperature Dependence of Tensile Properties of UNS N04400 Alloy

Effects of annealing and test temperatures on the tensile behavior of UNS N04400 alloy have been examined. The specimens were annealed at 800, 1000, and 1200xa0°C for 4xa0h under vacuum in a muffle furnace. Stress-strain curves of the specimens were obtained in the temperature range 25-300xa0°C using a universal testing machine fitted with a thermostatic chamber. The results indicate that the yield strength (YS), ultimate tensile strength (UTS), and percentage elongation of the specimens decrease with increase of annealing temperature. By increasing the test temperature, the YS and UTS decrease, whereas the percentage elongation initially decreases with increase of test temperature from 25 to 100xa0°C and then increases with further increasing the temperature up to 300xa0°C. The changes in the tensile properties of the alloy are associated with the post-annealing microstructure and modes of fracture.

Microstructural and Electrochemical Characterization of Ni/Ti2N Composite Coating for Sintered NdFeB Permanent Magnets

Sintered NdFeB magnets have complex microstructure that makes them susceptible to corrosion in humid or moist environments. The paper presents the anticorrosion characteristics of a novel Ni/Ti2N composite coating applied through electrodeposition and cathodic arc physical vapour deposition (CAPVD) to sintered NdFeB permanent magnets. The performance of composite coating was evaluated in simulated marine environment with the help of dc polarization techniques. The rate of coating degradation was also determined by employing ac electrochemical impedance spectroscopy (EIS). The coating morphology and surface chemistry were studied with scanning electron microscope (SEM). X-ray diffraction (XRD) was used for identification of component phases in the coating-substrate system. The results showed that the composite coating provided an adequately improved corrosion protection to the sintered NdFeB magnets in the simulated marine environment compared to the earlier reported ceramic and metallic coatings. The composite coating did not damage the magnetic properties of coating-substrate system that remained at par with the ceramic and nickel coating having copper interlayer.