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The fatigue behaviour of notched and unnotched specimens produced by additively manufactured Inconel 718 were analysed in the as‐built and heat‐treated conditions. The surfaces display high roughness and defects acting as fatigue initiation sites. In the as‐built condition, fine subgrains were found, while in in the heat‐treated state, the subgrains were removed and the dislocation density recovered. SN‐curves are predicted based on tensile properties, hardness and defects obtained by fractography, using the urn:x-wiley:ffe:media:ffe13300:ffe13300-math-0001‐method. © 2020 The Authors. Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Corrosion resistance of electrodeposited (ED) and electroless (EL) composite coatings have been a debatable issue in the published literature. The present paper aims to compare the corrosion resistance of ED Ni-B-Si3N4 composite coating with its plain counter part. The ED Ni-B coatings were prepared using Watt's nickel bath modified with the addition of dimethylamine borane and the ED Ni-B-Si3N4 composite coatings were prepared using the same bath in which Si3N4 particles (mean diameter: 0.80 ?m) were dispersed in it. The structural and morphological characteristics of ED Ni-B and Ni-B-Si3N4 composite coatings were determined using X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM). The corrosion resistances of ED Ni-B and Ni-B-Si3N4 composite coatings, both in as-plated and heat treated conditions, in 3.5% NaCl, were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies. The study reveals that the extent of shift in corrosion potential (Ecorr) towards the noble direction, decrease in corrosion current density (icorr), increase in charge transfer resistance (Rct) and decrease in double layer capacitance (Cdl) values with the incorporation of Si3N4 particles in the ED Ni-B matrix is not appreciable, both in as-plated and heat-treated conditions. The occurrence of the second phase angle maximum suggests penetration of the electrolyte via the pores/micro-pores in these coating to create another interface, namely, the electrolyte/substrate. Unlike the nanosized particles, the micron size Si3N4 particles (mean diameter: 0.80 ?m) used in this study is not capable of completely filling all the pores in the coating and allowed diffusion of chloride ions along the interface. The marginal improvement in corrosion resistance observed for ED Ni-B-Si3N4 composite coatings compared to its plain counterpart could have resulted from the decrease in effective metallic area prone to corrosion. � 2009 Elsevier B.V. All rights reserved.

A 5 kW continuous wave fiber laser welding system was used to deposit INCONEL® alloy 718 (IN718) on service-exposed IN718 parent metal (PM) substrates using filler wire addition. The microstructure of the deposits was characterized in the fully heat treated condition. The service-exposed IN718 PM and the direct laser deposited (DLD) specimens were then evaluated through room temperature tensile testing. The yield and tensile strengths were well above the minimum values, as defined in the aerospace specifications AMS 5596K and 5663M. However, the ductility at room temperature of the DLD and DLD-PM samples was slightly lower than that specified in AMS 5596K and 5663M. The tensile fracture surfaces of the service-exposed IN718 PM, DLD, and DLD-PM specimens were analyzed using scanning electron microscopy (SEM), and the tensile failure mechanisms are discussed in detail, particularly for the important roles of the secondary particles (MC carbides) and intermetallics (platelet Ni3Nb-δ and Laves phases).

Alloy 718 rods in two different heat treated conditions (solution treatment (ST) and ST followed by aging (STA)) were friction welded. The weld joints were subjected to two different post-weld heat treatments (direct aging (DA) and STA). Tensile tests were carried out at 650�C with an initial strain rate of 10-4s-1. Stress rupture tests were performed at 650�C at a constant load with an initial stress level of 690MPa. The ultimate tensile strength values for all conditions, expect for base material in ST condition and weld joints with prior ST or STA in the as-welded condition, were higher than the minimum value of 1000MPa specified by the Aerospace Material Specification for the base material in STA condition. The weld joint specimen in the as-welded state with prior STA condition failed in heat affected zone (HAZ). Though strengthening precipitates (?'') dissolved in weld metal and HAZ during welding, HAZ was weaker than weld metal due to coarser grains and so failure occurred in HAZ. In all other conditions, samples failed in base metal. The stress rupture properties such as minimum creep rate and time to rupture of the base material in ST condition and as-welded joints with prior ST or STA condition are almost same. The sample subjected to STA both before and after welding exhibits the best stress rupture properties. It may be attributed to homogenization as well as moderate coarsening of grain structure of weld zone and fine and uniform distribution of strengthening precipitates throughout the weldment. However, to obtain the best combination of tensile and stress rupture properties, the material should be welded in ST condition and it should be subjected to direct aging after welding. � 2014 Elsevier B.V.

A new superalloy, ATI 718Plus alloy (718Plus), has been developed to have a 55°C higher temperature capability over the traditionally used alloy 718, while maintaining favourable processing characteristics and intrinsic raw material costs. The fatigue and dwell fatigue behaviour of four microstructural variations of 718Plus are evaluated and compared with Waspaloy: standard heat treated condition (HT1), standard heat treated condition with thermal exposure at 732°C (1350°F) for 1000 h (HT2), fine grain condition with a modified d phase (HT3) and fine grain overaged through modified heat treatment (HT4). Fatigue crack growth rate tests were performed at 649°C (1200°F) and 704°C (1300°F) under constant amplitude loading at 10 Hz or with a 100 s tension dwell. The results show that the steady state fatigue crack growth rates of each microstructural variation and both alloys are identical, with all of the 718Plus variations showing a clear advantage over Waspaloy in the fatigue crack threshold regime. The 718Plus variants HT1 and HT3 exhibited the highest fatigue crack growth threshold, followed closely by HT4 and finally HT2. At 649°C (1200°F), the 718Plus alloys had average threshold values ranging from 8·8 to 10·4 MPa m1/2 whereas the Waspaloy material was 6·1-7·5 MPa m1/2. At 704°C (1300°F), the advantage increased with the 718Plus alloys having average threshold values ranging from 10·1 to 11·6 MPa m1/2 compared with Waspaloy, which exhibited average threshold values of 6·6-7·7 MPa m1/2. Dwell fatigue results show that Waspaloy has better resistance to crack propagation under dwell conditions; however, optimisation of the precipitate phase (HT2) shows vast improvement in the dwell fatigue resistance of 718Plus. © 2011 Canadian Institute of Mining, Metallurgy and Petroleum.

The problem of retention non-recrystallized grains elongated along rolling direction during processing of sheets of alloy TS6 (Ti-11Cr-5Mo-6V-3A1) exists for long time. By means of m etallographic, texture analyses and EBSD method, the formation and the retention of such grains was shown to be connected with texture inhibition. A number of features affecting on texture inhibition were characterized and classified. Main technological approaches to eliminate mentioned above non-recrystallized grains during the processing of sheet semi products were developed. These approaches made possible to obtain sheets with fine structure (D < 100 mkm) and high strength ratio in heat treated conditions.