Dissimilar P-TIG welding between Inconel 718 and commercially pure Titanium using niobium interlayer

The formation of brittle intermetallics is a challenge for the direct joining of commercially pure titanium (CpTi) and Inconel 718 (IN718) alloy. In the present work, dissimilar weldments using the P-TIG (Pulsed-Tungsten Inert Gas) welding technique were produced, with elemental Niobium (Nb) as an interlayer. The insertion of Nb acted as a barrier and suppressed the interdiffusion of Ti and Ni across the interlayer resulting in no TixNiy intermetallic compounds (IMCs) at the CpTi/IN718 dissimilar joint. Titanium (Ti) and Nb on CpTi side joined by solid solution (Ti, Nb) strengthening mechanism. Nickel (Ni) joined with Nb at IN718 side via eutectic reaction, where a diffused layer comprising of NbNi3, and Nb7Ni6 IMCs was found. Owing to the formation of brittle IMCs (NbNi3, Nb7Ni6), the diffused layer at Nb/IN718 interface exhibited the microhardness of ~782 HV, which is ~64 % higher than the Nb/CpTi interface and considered highest in comparison to the other regions of the joint. The maximum tensile strength of the weldment was 150 MPa, which is significantly less than CpTi (360 MPa) and IN718 (850 MPa) base alloys possibly due to the presence of cracks in the diffused layer and the welded joint

Investigating Nanoindentation Creep Behavior of Pulsed-TIG Welded Inconel 718 and Commercially Pure Titanium Using a Vanadium Interlayer

In a dissimilar welded joint between Ni base alloys and titanium, creep failure is a potential concern as it could threaten to undermine the integrity of the joint. In this research, the mechanical heterogeneity of a Pulsed TIG welded joint between commercially pure titanium (CpTi) and Inconel 718 (IN718) with a vanadium (V) interlayer was studied through a nanoindentation technique with respect to hardness, elastic modulus, and ambient temperature creep deformation across all regions (fusion zones and interfaces, mainly composed of a dendritic morphology). According to the experimental results, a nanohardness of approximately 10 GPa was observed at the V/IN718 interface, which was almost 70% higher than that at the V/CpTi interface. This happened due to the formation of intermetallic compounds (IMCs) (e.g., Ti2Ni, NiV3, NiTi) and a (Ti, V) solid solution at the V/IN718 and V/CpTi interfaces, respectively. In addition, nanohardness at the V/IN718 interface was inhomogeneous as compared to that at the V/CpTi interface. Creep deformation behavior at the IN718 side was relatively higher than that at different regions on the CpTi side. The decreased plastic deformation or creep effect of the IMCs could be attributed to their higher hardness value. Compared to the base metals (CpTi and IN718), the IMCs exhibited a strain hardening effect. The calculated values of the creep stress exponent were found in the range of 1.51–3.52 and 2.52–4.15 in the V/CpTi and V/IN718 interfaces, respectively. Furthermore, the results indicated that the creep mechanism could have been due to diffusional creep and dislocation climb

Machining of carbon steel under aqueous environment: Investigations into some performance measures

In this study, a new machining approach (aqueous machining) is applied for mill machining and its performance is compared with traditional wet machining. AISI 1020 steel is employed as the test material and Taguchi statistical methodology is implemented to analyze and compare the performance of the two machining approaches. The cutting speed, feed rate, and depth of cut were the machining parameters used for both types of machining, while the selected response variables were surface roughness and hardness. Temperature variations were also recorded in aqueous machining. Compared with wet machining, aqueous machining resulted in lower surface roughness (up to 13 %) for the same operating conditions and about 14 % to 16 % enhancement in hardness due to the formation of finer pearlite, as revealed by the microstructure analysis. Compared to the parent unmachined surface, the hardness of machined surfaces was 24 % to 31 % higher in wet machining and 44 % to 51% higher in aqueous machining. Another benefit of aqueous machining was the energy gain, which ranged from 718 to 8615.96 J. This amount of heat energy can be used as waste heat for preheating domestic hot water, running the organic Rankine cycle with waste heat and preheating the inlet saline water for desalination, vacuum desalination, etc. If successfully implemented in the future, this idea will provide a step towards achieving sustainable machining by saving lubricants and toxic wastes in addition to saving energy for secondary applications

Effect of raster angle and infill pattern on the in-plane and edgewise flexural properties of fused filament fabricated acrylonitrile–butadiene–styrene

Fused Filament Fabrication (FFF) is a popular additive manufacturing process to produce printed polymer components, whereby their strength is highly dependent on the process parameters. The raster angle and infill pattern are two key process parameters and their effects on flexural properties need further research. Therefore, the present study aimed to print test specimens with varying raster angles and infill patterns to learn their influence on the in-plane and edgewise flexural properties of acrylonitrile–butadiene–styrene (ABS) material. The results revealed that the highest in-plane and edgewise flexural moduli were obtained when printing was performed at 0 ° raster angle. In comparison, the lowest values were obtained when the printing was executed with a 90 ° raster angle. Regarding the infill pattern, the tri-hexagon pattern showed the largest in-plane modulus, and the quarter-cubic pattern exhibited the greatest edgewise flexural modulus. However, considering both the modulus and load carrying capacity, the quarter-cubic pattern showed satisfactory performance in both planes. Furthermore, scanning electron microscopy was used to investigate the failure modes, i.e., raster rupture, delamination of successive layers and void formation. The failure occurred either due to one or a combination of these modes

Investigating the bonding mechanism of P-TIG welded CpTi/Inconel 718 dissimilar joint with Nb interlayer

The direct joining of CpTi and Inconel 718 is challenging due to the formation of brittle TixNiy in the fusion zone. For the TIG welding of CpTi/IN718 joints in the present work, the use of Nb as an interlayer served as a barrier, resulting in the complete suppression of brittle TixNiy which is responsible for immediate failure of the CpTi/IN718 dissimilar joint. The results indicated that solid solution formed towards the CpTi side, whereas eutectic formation (NbNi3, Nb7Ni6) was observed towards the In718 side of the weldment. Owing to these brittle IMCs, a nanohardness of ∼14.62 GPa was measured at the Nb/IN718, which is ∼70% higher than that of the Nb/CpTi interface which was comprised of columnar dendrites. The tensile strength was 150 MPa with the presence of cleavage cracks at the Nb/IN718 interface of the fractured surface

Relationship between microstructure and nanomechanical properties in Dissimilar Friction- Stir- Welded AA6061-T6 aluminum alloy and AISI 316 stainless steel

Friction- stir- welding (FSW) has emerged as a unique joining method to weld dissimilar materials (DMs). The objective of the present study is to investigate the evolved microstructure, surface hardness (H), and elastic moduli (E) in different weld- regions of the FSW butt welded aluminum alloy (AA6061-T6) and stainless steel (AISI 316). The results revealed that the welding process softened the Al alloy in the stir zone and produced significant hardness in the steel because of recrystallization, dissolution of precipitates and the formation of extremely fine equiaxed grains in the weld nugget. The % elastic recovery from load -displacement curves showed elastic to plastic deformation to a depth of <400 nm

Nanomechanical, mechanical and microstructural characterization of electron beam welded Al2219-T6 tempered aerospace grade alloy: A comprehensive study

As compared to traditional fusion welding processes, electron beam welding (EBW) is known to produce structurally robust microstructures and narrow heat-affected zone (HAZ) in metals. The process becomes more significant for the tempered alloys vulnerable to heat exposure. In the present investigation, Al 2219-T6 alloy was joined using the EBW process. The microstructural, mechanical, and nanomechanical characteristics of the resulting joint were investigated. EBW resulted in a narrow HAZ (22 μm) with a 430 mm fusion zone (FZ). A dendritic structure was observed in the FZ zone, while second-phase particles were absent indicating their dissolution during welding and interesting formation of Al2Cu mixture around the dendrites. The limited content of Cu in the base metal (BM) resulted in the formation of a solid solution in the FZ, along with the presence of fine equiaxed grains in the HAZ and equiaxed dendritic grains in the FZ zone. The X-ray diffraction analysis confirmed the absence of peaks corresponding to incoherent phases in the FZ. Compared to the BM, micro-hardness measurements revealed a 12.7 % increase in the hardness in the HAZ, while a significant decrease of approximately 19 % was observed in the FZ. The joint exhibited reduced tensile strength, ultimate strength by 42.2 %, and yield strength by 47.3 % when compared to the BM. The fracture analysis indicated a ductile failure mode with the presence of microvoids. Nano-indentation tests at various loads demonstrated a decrease in the nanohardness from the BM to the HAZ and FZ regions. Atomic force microscopy (AFM) analysis revealed significant pile-ups in the FZ, indicating the occurrence of plastic deformation during the welding process. The presented findings are valuable for the joint and structure design of Al −2219T6 alloy in particular and other Al alloys in general

Evaluation of nano indentation behavior of TIG, MIG and diffusion bonded Inconel 718 and austenitic Stainless Steel 316L joint interface

The nanomechanical characteristics of Metal Inert Gas (MIG), Tungsten Inert Gas (TIG), and diffusion-bonded Inconel (IN718) and Austenitic Stainless Steel (SS 316L) were investigated. The nano hardness and elastic modulus of different weldments were evaluated using nanoindentation and compared. The results showed that intermetallic compounds (IMCs) and carbides were reduced with diffusion bonding. Moreover, maximum nano hardness and elastic modulus occurred in the welded zone (WZ) of TIG and MIG welded joints while at the bonding interface in diffusion bonding (DB). Lastly, the nano hardness of the bonding interface in diffusionbonded was 11 % and 7 % lower compared to MIG and TIG welded joints

Microstructural and Mechanical Characterizations of Mo/W and Mo/Graphite Joints with BNi2 Paste

Brazing of Mo to W and to graphite is achieved using BNi2 paste (containing Ni, Cr, Si, and B). For the Mo/W or Mo/graphite joint, the joining area consists of a diffusion area and a brazing area. The diffusion area is composed of MoNi and Mo, which is formed by diffusion of the Mo substrate into the braze during brazing. The brazing area of the Mo/W joint contains Ni(ss) (solid solution), Cr(ss), Ni3B, CrB, and Ni4W, while the brazing area of the Mo/graphite joint mainly comprises Ni(ss), MoNi, Ni3B, and CrB. A continuous chromium carbide layer is formed at the brazing area/graphite interface in the Mo/graphite joint due to the reaction of Cr in the BNi2 braze with the graphite. Nanoindentation measurements of the joints show that the diffusion area exhibits the highest hardness and elastic modulus in the joints. The shear strengths of the Mo/W and Mo/graphite joints are 58.1 ± 16.0 and 13.0 ± 4.0 MPa, respectively. The Mo/W and Mo/graphite joints fracture after the shear tests in the W and graphite sides, respectively, near the joining area, indicating that both fractures are caused by the stress concentration in the corresponding areas