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Nickel based alloy was fabricated by a laser powder bed fusion using the blue laser with the wavelength of 450 nm and maximum output power of 200 W, and the effect of volumetric energy density (VED), on the porosity was evaluated for fabricated samples. A fabricated sample using the blue diode laser, recorded a porosity of 0.012% at the VED of 33 J/mm3, indicating that it can be fabricated more efficiently than the sample fabricated using the near-infrared fiber laser. Furthermore, it was revealed that when the surface roughness of the fabricated sample reached 37.5 μm, large voids were generated, indicating a high likelihood of void formation at a surface roughness of approximately 40 μm or more during the layer-by-layer fabrication of nickel-based alloys using the blue diode laser in powder bed fusion. [ABSTRACT FROM AUTHOR]

Microstructure evolution and microindentation properties of dissimilar weld between Inconel 625 nickel based alloy and UNS S32205 Duplex Stainless Steel have been investigated in the current study. Samples in cross-section areas were prepared to investigate microstructure and micromechanical properties in different regions of weld using optical microscopy, scanning electron microscopy and indentation measurements. Typical solidification microstructures were observed. Secondary phases were noticed in both the weld metal and heat affected zone of Inconel 625 alloy at cellular and interdendritic region in lamellar, rod shaped and cuboidal form. These secondary phases were identified as Laves phase and carbonitrides of Nb and Ti. Mechanical properties including elastic modulus and hardness were estimated across the weld joint. The results showed that the weld metal exhibit the lowest values of hardness and elastic modulus, however the Heat Affected Zone of the stainless steel exhibit the highest values owing to high δ-ferrite amount. In-situ nanoindentation coupled with Scanning Electron Microscope was carried out in Laves phase and the matrix weld in order to evaluate nanohardness. The result showed that the nanohardness of Laves phase is too great compared to the weld matrix. [ABSTRACT FROM AUTHOR]

While nickel based alloys possess great chemical attraction and very low thermal conductivity, their machining is very complex. Shorter tool life with high wear is quite obvious during turning of these alloys, due to excessive friction and temperature. With the intention of increasing tool life, cryogenic treatment followed by tempering was carried out on multilayer coated inserts. The treated and tempered inserts were compared with the untreated ones for dry turning of Inconel 718 alloy. The outcome revealed that the tempered inserts outperformed the untreated and treated ones while investigating tool wear and cutting forces. In addition, the tempered inserts exhibited higher scratch resistance and lower chip tool contact distance. [ABSTRACT FROM AUTHOR]

While nickel based alloys possess great chemical attraction and very low thermal conductivity, their machining is very complex. Shorter tool life with high wear is quite obvious during turning of these alloys, due to excessive friction and temperature. With the intention of increasing tool life, cryogenic treatment followed by tempering was carried out on multilayer coated inserts. The treated and tempered inserts were compared with the untreated ones for dry turning of Inconel 718 alloy. The outcome revealed that the tempered inserts outperformed the untreated and treated ones while investigating tool wear and cutting forces. In addition, the tempered inserts exhibited higher scratch resistance and lower chip tool contact distance. [ABSTRACT FROM AUTHOR]

The investigations on fretting wear behaviors of nickel based alloy in NaCl solution and atmosphere indicated that wear mechanism and regional transformation from partial slip regime (PSR) to the mixed regime (MR) are significantly affected by NaCl solution. The crevice corrosion induced by synergy of chloride ion and deformed asperities caused wear mechanism changed from adhesive and oxidation wear (PSR in atmosphere) to abrasive and oxidation wear (PSR in NaCl solution) and to oxidation and delamination wear (MR in NaCl solution), meanwhile accelerated the regional transformation from PSR to MR. However, the annular fatigue crack was almost unaffected by NaCl solution, which propagated along the direction of 40-50° to surface in the mode of transgranular and intergranular in all conditions. [ABSTRACT FROM AUTHOR]

MgCl2-KCl binary system has been proposed to be used as high temperature reactor coolant. Due to its relatively low melting point, good heat capacity and excellent thermal stability, this system can also be used in high operation temperature concentrating solar power generation system as heat transfer fluid (HTF). The corrosion behaviors of nickel based alloys in MgCl2-KCl molten salt system at 1,000 °C were determined based on long-term isothermal dipping test. After 500 h exposure tests under strictly maintained high purity argon gas atmosphere, the weight loss and corrosion rate analysis were conducted. Among all the tested samples, Ni-201 demonstrated the lowest corrosion rate due to the excellent resistance of Ni to high temperature element dissolution. Detailed surface topography and corrosion mechanisms were also determined by using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). [ABSTRACT FROM AUTHOR]

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Bonding of ceramic to the alloy is essential for the longevity of porcelain fused to metal restorations. Imported alloys used now a days in processing them are not economical. So this study was conducted to evaluate and compare the bond strength of ceramic material to nickel based cost effective Nonferrous Materials Technology Development Center (NFTDC), Hyderabad and Heraenium S, Heraeus Kulzer alloy. An Instron testing machine, which has three-point loading system for the application of load onto the specimen was utilized for analyzing bond strength of both alloys. Student t test was conducted and t value obtained was 0.644, and the mean value of flexural bond strength of indigenous alloy is 81.75 with standard deviation of 12.25 and of imported alloy is 84.42 with standard deviation of 10.35, indicating that there was no significant difference between the two alloys. Due to ever increasing cost of imported non-precious alloy the need for a cost-effective replacement was fulfilled by indigenous NFTDC alloy. [ABSTRACT FROM AUTHOR]

Ta was added to laser clad NiCrBSi coating to improve wear resistance. In situ synthesised TaC particles of nearly equiaxed shape were uniformly dispersed in the coating. The colony that contained acicular Cr rich boride or carbide grew radially around the TaC particle and had a strong bond with the particle. The TaC particles had good bonds with the matrix, and tended to be crushed and impressed into the matrix instead of being pulled out from the wear surface during the wear process. The NiCrBSi+Ta coating exhibited higher fracture toughness, and higher abrasive and adhesive wear resistance than the NiCrBSi coating. The primary wear mechanism of the NiCrBSi+Ta coating was abrasion combined with the oxidation process under all test conditions while the main wear mechanism of the NiCrBSi coating was abrasion and microflaking under a low load (30 N), and adhesion and oxidation under a high load (75 N). [ABSTRACT FROM AUTHOR]

In the present work, the plasma nitriding behavior of a nickel based dental alloy was investigated. Plasma nitriding experiments carried out under constant gas mixture (15% H-85% N) for different process parameters including time (4, 6, 10, and 20 h) and temperature (400, 450, 500, and 550 °C). Depending on nitriding parameters, it was found that triple or double layers formed on the surface of the samples. Increasing of treatment time and temperature has resulted in a double layer. γ layer was in formed all nitrided samples. However, γ layer is formed only at low temperatures and in short times. Layer growth of nickel based alloys increases until a critical time or a critical temperature reached. Above these critical values, it is observed that the layer thickness decreases. It was also found that plasma nitriding not only increases the surface hardness but also improves the wear resistance of nickel based dental alloy. The maximum wear resistance was observed at 400 °C for 10 h due to the high hardness and thickness of the nitride layers. [ABSTRACT FROM AUTHOR]

Nickel based hardfacing alloys Colmonoy-5 and Colmonoy-6 deposited on type 316L austenitic stainless steel substrate using the gas tungsten arc welding process, were characterised for their microstructure and hardness variations across the deposit/substrate interface, and for identification of the principal precipitates present in these hardface deposits. Hardness measurements and electron probe microanalysis (EPMA) across the interface revealed the presence of a dilution zone 2·5 mm wide in the Colmonoy-6 deposit and 1·5 mm wide in the Colmonoy-5 deposit. EPMA and X-ray diffraction studies of the precipitates showed that he blocky type precipitates were chromium borides and the needle-like precipitates were chromium carbides. Also, stress relief heat treatment at 1123 K for 4 h was found to have no significant effect on the hardness of these hard face deposits. [ABSTRACT FROM AUTHOR]