Analysis on Bonding Interface during Solid State Additive Manufacturing between 18Cr-8Ni and 42CrMo4 High Performance Alloys

The need for additive manufacturing (3D printing) to create near net shape components from a wide variety of materials has grown in recent years. There are several additive manufacturing methods to build various parts by different materials. However, it is challenging to construct, the components with incompatible materials combination for high temperature and creep resistance using conventional methods. Consequently, the purpose of this research is to investigate the use of solid state welding (friction welding) in additive manufacturing (SSAM) of incompatible materials, namely alloy Cr18-Ni8 and 42CrMo4 low alloy alternative layers. The interface bonding strength must be strengthened to achieve the desired isotropic characteristics and high strength for the components. Due to the low temperature at the bonding interface, secondary phases cannot develop when solid state welding is used. In order to obtain the highest bonding strength, optimal process parameters were examined using design of experiments (DOE) with Box–Behnken design model and analysis of variance (ANOVA). The major process parameters of upset pressure, friction pressure and burn-off length were varied to obtain the optimal conditions. In addition, the bonded interfaces were examined by the microstructural characteristics as well as mechanical properties such as micro-hardness and bonding strength. The interface is made up of alloys intermixed with different zones such as a dynamically recrystallized zone and a thermomechanical affected zone. The intermixed layers revealed the migration of C and Mo to Cr18-Ni8 alloy and separated the Fe and Ni bands. The fractography analysis revealed ductile and slightly brittle fracture surfaces with a mixed mode. The relationship between bond strength and interface thickness was determined by studying the impact of interface thickness on bond strength

Discrete wavelet analysis of mutually interfering co-existing welding signals in twin-wire robotic welding

The article presents new findings on arc stability in twin-wire robotic arc welding corresponding to the torch orientation and electrodes' position. The two mutually influencing co-existing arcs affect the stability of counterpart arc, and thereby alter the weld bead properties. The complex interaction between the arcs is determined by multi-resolution time-frequency spectrum using wavelet analysis. The wavelet-energy-entropy of the signals are analyzed to quantify the arc stability. Several experiments are conducted with different combinations of welding currents at primary and secondary electrodes (vis-a-vis one who initiates and follows the arching sequence, respectively) in tandem and transverse orientation of the torch. The investigation divulges that electrode positions and torch orientation significantly impact arc stability which in turn impacts the heat input and weld bead geometry. The arc penetration in tandem orientation is augmented by the secondary arc that operates in the same weld pool. While the transverse orientation improves the arc stability and facilitates a wider weld bead with reasonable weld penetration suitable for applications such as wire additive manufacturing and cladding. An approach for predicting arc stability as a function of process parameters is a significant contribution from this investigation. The insight into the arching phenomenon in twin-wire gas metal arc welding due to the investigation is expected to help the machine builders to design an appropriate controller that minimizes arc interference

Discrete wavelet analysis of mutually interfering co-existing welding signals in twin-wire robotic welding

status: Published onlin

Characterization of Microstructural Anisotropy in 17–4 PH Stainless Steel Fabricated by DMLS Additive Manufacturing and Laser Shot Peening

The present study aims to produce the additive manufacturing of precipitation-hardened 17-4 PH stainless steel with isotropic microstructure using direct metal laser sintering (DMLS). The deposits' microstructure and surface properties were modified to improve their physical properties. The required surface modification has been obtained by applying shot peening strain-hardening effect on the deposited layers. Microstructure and mechanical properties were enhanced by using shot peening. Results revealed that the microstructure of the DMLS deposits was strain hardened and modified with the presence of a fine grain structure. The grain size analyses by electron backscattered diffraction (EBSD) indicated the nearly isotropic microstructure in the deposits along with the build-up direction (Z-axis) and transverse direction (XY directions) with the presence of equi-axed microstructure. The mechanical properties of the DMLS deposits were evaluated to determine the hardness, tensile strength, yield strength, and elongation. The results revealed that the properties obtained for both directions are nearly the same. The strength of the deposits was further improved by applying heat treatment techniques

Advances in hydrogen-enriched biogas/biodiesel combustion for near-zero emissions in direct injection engines

Alternative fuels like biogas, biodiesel, and hydrogen are gaining traction as sustainable solutions to reduce fossil fuel dependency and mitigate environmental pollution. This review examines the performance, combustion, and emission characteristics of compression ignition dual-fuel diesel engines utilizing these fuels. Key performance indicators, including brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), peak cylinder pressure (PCP), ignition delay, and emission metrics carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), particulate matter (PM), and carbon dioxide (CO2), are thoroughly analyzed. Biogas usage leads to a 2–20 % reduction in BTE, up to 35 % higher BSFC, and an 18–55 % decrease in NOx and smoke emissions, but increases HC and CO emissions by up to 30 %. In compare, hydrogen and biodiesel improve BTE by up to 10 %, reduce HC and CO emissions by 40–50%, but increase NOx emissions by 20 %. Biogas exhibits lower PCP (10–15 %), flame temperature (1600–1800 K), and extended burn duration (40–50 °CA). Biodiesel demonstrates moderate PCP (5–10 %), flame temperature (2000–2200 K), and shorter burn duration (35–40 °CA). Hydrogen outperforms both fuels with the highest PCP (15–20 %), flame temperature (2300–2500 K), and rapid burn duration (25–30 °CA), achieving combustion efficiency greater than 95 %, albeit with elevated NOx levels. These findings highlight the potential of alternative fuels to enhance engine performance, optimize combustion characteristics, and reduce harmful emissions, contributing to cleaner energy and sustainable development

Effect of Post-Weld Heat Treatment Cooling Strategies on Microstructure and Mechanical Properties of 0.3 C-Cr-Mo-V Steel Weld Joints Using GTAW Process

A total of 0.3%C-Cr-Mo-V steel, a high-strength alloy steel widely used in rocket motor housings, suspension systems in high-performance vehicles, etc., is noted due to its high strength-to-weight ratio. However, its high carbon equivalent (CE > 1%) makes it challenging to weld, as it is prone to brittle martensitic formation, which increases the risk of cracking and embrittlement. The present paper focuses on enhancing the microstructure and mechanical properties of 0.3% C-Cr-Mo-V steel by gas tungsten arc welded (GTAW) joints, utilizing post-weld heat treatment and cooling strategies (PWHTCS). A systematic experimental approach was employed to ensure a defect-free weld through dye penetrant testing (DPT) and X-ray radiography techniques. Subsequently, test specimens were extracted from the welded sections and subjected to PWHT protocols, including hardening, tempering, and rapid quenching using air and oil cooling (AC and OC, respectively) mediums. Results show that OC has enhanced tensile strength and hardness while simultaneously maintaining and improving ductility, ensuring a well-balanced combination of strength and toughness. Fractography analysis revealed ductile fracture in AC samples, whereas OC weldments exhibited a mixed ductile–brittle fracture mode. Thus, the findings demonstrate the critical role of PWHTCS, with OC, as an effective method for achieving enhanced mechanical performance and microstructural stability in high-integrity applications

Synergistic Effects of Thermal Cycles and Residual Stress on Microstructural Evolution and Mechanical Properties in Monel 400 and AISI 316L Weld Joints

The current study investigates the thermal, metallurgical, and mechanical results in similar and dissimilar weldments of Monel 400 and AISI 316L. Infrared thermography (IRT) was employed to record thermal cycles, while X-ray diffraction (XRD) was used to analyze the residual stresses post-welding. Mechanical properties were assessed through tensile and microhardness tests, and microstructural evolution was examined using energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). IRT results showed peak temperatures of 1788 °C for Monel 400 and 1750 °C for AISI 316L. Residual stress analysis revealed compressive stresses of 293 MPa in dissimilar welds, compared to 235 MPa in Monel 400 and tensile stresses of 57 MPa in AISI 316L. Ultimate tensile strength (UTS) values were 543 MPa for dissimilar welds, 533 MPa for Monel 400, and 556 MPa for AISI 316L, with corresponding microhardness values of 207 HV, 203 HV, and 168 HV, respectively. Microstructural analysis identified coarse Ni-Cu phases in the Monel 400 heat-affected zone (HAZ), austenitic structures in AISI 316L, and intermetallic compounds in dissimilar welds. The findings highlight the impact of thermal distribution, residual stress, and microstructural evolution on weld performance, providing insights into optimized welding parameters for improved joint integrity and mechanical properties