This book provides in-depth analysis and discussion of cracking phenomena associated with welding and additive manufacturing. Experts from around the world have contributed papers that describe cracking phenomena in a wide range of engineering materials, including steels, stainless steels, nickel-base alloys, and other nonferrous alloys. Cracking during both welding and additive manufacturing is presented and discussed. This proceedings follows from four previous conferences on the topic of cracking in welds and expands the focus to cracking associated with additive manufacturing processes.

Two 617-type filler metals with different Carbon and Boron contents were used to deposit TIG all-weld metal. Longitudinal Varestraint testing was utilized to evaluate and compare their weld metal cracking susceptibility. Hardness, tensile, and impact toughness testing were conducted on the all-weld metal samples, and light optical microscopy as well as scanning electron microscopy, equipped with energy dispersive spectroscopy were adopted for the microstructural inspection of the Varestraint tested samples. Computational thermodynamics supported in calculating the solidification interval and predicting the phases formed. Results showed that the modified Alloy 617 (617mod.) with higher Boron and lower Carbon content is the preferred filler metal, because it showed lower hot cracking susceptibility than the regular version of Alloy 617. In addition, the impact toughness of the modified Alloy 617 was almost three times higher than for Alloy 617 but showed lower tensile strength. In terms of microstructure, the modified Alloy 617 disclosed less precipitates along the cracks than the regular Alloy 617. These observations were supported by computational thermodynamic calculations.

Economic and environmental sustainability, together with flexibility in education, are the main driving forces for integrating virtual reality laboratories into welding education. A multidisciplinary team consisting of welding educators and immersive computing researchers developed a virtual reality laboratory focused on teaching welding processes and welding metallurgy. Fifty students in manufacturing engineering used the virtual laboratory in seven courses offered over 18 months, and 20 educators attended informative and training sessions. The virtual reality laboratory was continuously improved based on the feedback received from students and educators during that period, and the main goal in this work was to assess the eventual benefits of the virtual reality laboratory as an educational tool versus the real campus laboratories. In terms of effectiveness, 74% of the students considered the virtual reality laboratory to be an effective learning tool.

However, when the students were asked if physical laboratories should be replaced by virtual ones, most wanted to continue with physical laboratories, seeing the virtual laboratory as a complementary tool offering additional learning opportunities. Interestingly, despite educators unanimously agreeing on the benefits of the tool, resistance to implementing the tool in their courses was observed.

The applicability of additive manufacturing (AM) of duplex stainless steels has been limited by the complex thermal history causing an imbalance of ferrite and austenite in the as-deposited material. Laser-beam directed energy deposition with wire (DED-LB/w) presents a promising solution when combined with solution annealing. This study utilizes a specially developed 3Dprint AM 2205 and a conventional ER2209 wire to continuously build cylindrical components. Metallographic examination was conducted using light optical microscopy (LOM), scanning electron microscopy (SEM) with energy dis- persive spectroscopy (EDS), electron backscatter diffraction (EBSD), and electron microprobe analysis (EPMA). While high deposition rates were achievable, excessively high wire feeding rates led to continuous areas of fine grains in the deposited beads. These regions, identified as partially molten wire, were sometimes associated with lack-of-fusion, porosity, and solidification cracking. Optimized parameter settings enabled efficient melting of the wire, producing defect-free deposits, and eliminating partially molten wire residues. Solution annealing effectively dissolved intermetallics and homogenized the microstructure, resulting in a more uniform phase distribution.

Recently developed FeCrAl alloys could be an economical alternative to nickel-based alloys in overlay welds for the power generation industry. However, more investigation on their microstructure and properties is needed at temperatures for boiler applications. This work compared the performance of three FeCrAl alloys (EF100, EF101, and APMT) as overlay welds, in as-deposited condition and after being exposed for 6 months in a CFB boiler’s evaporator tube bank. Bending, high temperature tensile test, restraint-cooling test, hardness, fractography, microscopy, microanalysis, and atom probe tomography (APT) were used. The results showed a ranking for ductility, being EF100 > EF101 > APMT. A high ductile-to-brittle transition temperature, below 100 °C, confirmed the low ductility and high cold cracking susceptibility. The microstructural analysis was in line with the previous grading. For APMT, APT showed that the exposure of the alloy at 400 °C for 11 days resulted in higher Cr concentration around carbides than in the matrix. This suggests that carbides could be initiation sites pushing toward the α-phase separation (Fe-rich vs Cr-rich), explaining the hardening and resulting in a drastic reduction in the ductility of APMT overlay welds.

The use of additive manufacturing, especially laser beam powder bed fusion (PBF-LB), is becoming increasingly popular for producing super duplex stainless steel (SDSS) parts. However, the rapid cooling rate, complex thermal cycles, and eventual nitrogen loss during processing can result in an unbalanced ferritic microstructure and the formation of intermetallics; hence, solution annealing heat treatment following the PBF-LB process is required. The present study aims to compare the as-built and heat-treated microstructures of 2507 SDSS manufactured via PBF-LB with varying solution annealing times. Computational thermodynamics were used to establish the solution annealing temperature (CALPHAD) and time (DICTRA). The as-built microstructure comprises predominantly ferrite, intragranular chromium nitrides with a small amount of grain boundary, and intragranular austenite. The experimental results showed the formation of a balanced two-phase ferrite and austenite microstructure within 2 min of solution annealing time, in good alignment with the DICTRA calculations. This microstructural balance was maintained with increased solution annealing time up to 60 min. The solution-annealed microstructure revealed the dissolution of intragranular chromium nitrides, the growth of grain boundary austenite, and the formation of intragranular and Widmanstätten austenite. This study exemplifies how computational thermodynamics can be successfully used in the design of solution annealing heat treatment for 2507 SDSS manufactured via the PBF-LB process.

The PH 13-8 Mo family of steels belong to the martensitic precipitation hardening stainless steels (MPHSSs) category, which exhibits a good combination of mechanical properties and corrosion resistance. Additive manufacturing (AM) offers advantages, including reduced material waste and the capability to produce complex, near-net-shape parts. Consequently, the application of AM techniques to the PH 13-8 Mo family is being increasingly explored across various industries. This review paper presents the existing literature on the topic and provides an overview. The review starts by presenting information about the PH 13-8 Mo family, including microstructure, chemical compositions, heat treatments, and mechanical properties. Afterwards, the work focuses on presenting the microstructure and resulting properties of PH 13-8 Mo family processed by three different additive manufacturing processes: Powder Bed Fusion using a Laser Beam (PBF-LB), Directed Energy Deposition using an Electric Arc (DED-Arc), and Directed Energy Deposition using a Laser Beam (DED-LB), both in their as-built condition and following post-processing heat treatments. The review concludes with a summary and outlook that highlights existing knowledge gaps and underscores the need for further research to tailor the microstructural evolution and enhance the properties. The findings indicate that AM of the PH 13-8 Mo family has the potential for industrial applications, yet further studies are necessary to optimize its performance.

The integration of virtual reality (VR) laboratories into welding education presents an array of potential advantages. It can be used at campus or in distance, and it offers an alternative when access to traditional laboratories is challenging. The economic benefits, including savings on material preparation and energy costs, along with the environmental, health and safety advantages of mitigating exposure to welding fumes, arc radiation, and electrical hazards, add further value and contribute to sustainability in welding education. The work presented here is an example of the integration of education in the areas of welding and informatics and research on immersive learning. A multidisciplinary team worked on the development of an immersive learning environment, including virtual laboratory areas for welding processes as well as for microstructural inspection of welds.

During the project, this learning environment, and the contained virtual laboratories, have been implemented by the researchers with the support from IT students, and tested, and improved with the feedback provided by students in welding technology, materials science, and manufacturing courses. Overall, more than twenty students from Informatics have been involved throughout the project, resulting in five bachelor theses, three master theses, three course projects in Immersive computing, and two course projects focusing on web development. The involvement of IT students has not only supported the development of the virtual learning environment, but it has also created new avenues for future research and developments in immersive computing.

Three FeCrAl alloys (APMT, EF100 and EF101) from Kanthal® and the reference Ni‐Cr Alloy 625 were used as weld cladding materials on tube shields in the evaporator tube bank of a waste‐fired combined heat and power plant.

For each alloy type, the overlay welded tube shields were placed in both roof and floor positions within the evaporator for 6 months. The metal‐loss rate, the microstructure and hardness of the overlay welds before and after exposure and the corrosion products were analysed.

The results showed higher metal‐loss rates in the welds placed in the roof position, confirming heterogeneities in the evaporator bank environment. Alloys were ranked from higher to lower erosion–corrosion resistance as follows: APMT≈Alloy 625 > EF101 > EF100.

The analysis of the corrosion attacks showed a significant variation among the alloys, from a primarily homogeneous corrosion attack on APMT tointergranular corrosion in EF100 and pit formation in EF101.