This paper presents the development of a modified tool steel (X30CrMnMoN13-3-1) specifically designed for defect-free processing via laser powder bed fusion (LPBF) without requiring complex machine modifications. The research addresses the dual challenge of carbon-containing tool steels in additive manufacturing: maintaining wear resistance while preventing cracking. Through optimization of the alloying system—particularly with carbon, nitrogen, chromium, molybdenum, and manganese—and the use of moderate preheating (150 °C), the authors achieved crack-free components with hardness levels up to 57 HRC after appropriate heat treatment.

This paper aims to develop a multiparameter-based three-dimensional simulation tool for cold spray, designed to predict material deposition behavior in real-world processes under varying process parameters and workpiece geometries.

In this research work, MoNbZrTiV and AlNbTaTiV refractory high-entropy alloy (RHEA) material combinations were investigated as potential candidates for feedstock materials for cold spray additive manufacturing. The two RHEA materials as precursors for developing micron-sized particles were alloyed mechanically through high-energy ball milling following a rigorous material design-of-experiments curriculum on account of elemental melting point differences. Detailed particle characterization techniques were employed to gain insights into the RHEA particle properties.

The objective of this study was to quantitatively investigate the build-up of residual stresses in selective laser-melted 316L stainless steel samples and identify the nature of the stresses. In addition, the effectiveness of stress relief heat treatment in reducing residual stresses or changing their characteristics was examined. The results were compared against those obtained from conventionally hot-rolled 316L samples.

This article describes advanced techniques used in the repair and refurbishment of a platform combustion system (PCS) for an SGT5-8000H turbine. The first part outlines the refurbishment process of the part basket—a key PCS component—covering inspection, repair, recoating, and final assembly steps. The second part highlights the integration of advanced repair technologies, including laser-based cutting and welding, as well as patch repairs using 3D-printed parts via laser powder bed fusion.

This work aims to evaluate the viability of laser heat treatments as a method to recover cold-sprayed coating ductility, i.e., to achieve with laser heat treatment a gain in elongation equivalent to a furnace heat treatment. A 4kW YAG laser was employed to heat treat 4-5 mm thick coldsprayed copper coatings produced on coupons and on prototypes of large components. Surface temperatures were monitored during the heat treatment using an infrared camera. Hardness and tensile properties were measured on as-sprayed and heat-treated coatings. Microstructural examinations provided additional insights to explain the properties evolution during heat treatment.

This paper proposes a new procedure for preparing enameled steels by thermal spraying the ceramic enamel followed by laser sintering and vitrification to obtain a smooth, corrosion-resistant, and anti-fouling coating. This study investigated the influence of enamel formulation, spraying methods, and laser parameters on the coating properties and characteristics, including microstructure, topography, phase composition, mechanical stability, and laser vitrification.

This study focuses on a novel online cold spray process monitoring system that uses in-situ diagnostics during cold spraying and cold spray additive manufacturing. It combines the in-flight behavior of particles with the expected properties of the resulting coatings.

This study focuses on the deposition and post-processing behavior of commercially pure copper produced using cold spray additive manufacturing (CSAM) with compressed air. By evaluating the microstructural evolution and mechanical performance of as-deposited and heat-treated copper samples, this work aims to provide insights into optimizing CSAM processes for industrial applications.

Restoring the damaged shaft parts to extend their service life is an economical and environmentally friendly solution. In recent years, the laser metal deposition (LMD) process has received increasing attention in component restoration. However, the residual stress and deformation inevitably occur due to the heat input, leading to the deflection of the repaired shafts. Therefore, this study aims to minimize the deflection of LMD-repaired shaft parts through parameter optimization. The width and height of the LMD deposit as a function of the laser power and traverse speed were achieved by fitting a series of one-pass experimental results. Based on it, the finite element analysis was conducted to clarify the effect of the repairing conditions (e.g., laser power, traverse speed, and initial substrate temperature) on the deflection and residual stress distribution of the shaft parts after LMD repairing. A 304 stainless steel round bar with a diameter of 6 mm was served as the component to be repaired. The deposit was 316L stainless steel, whose deposition process was realized by the element birth and death technique. The results indicated that the free-end of the specimen experienced complicated deformation during the LMD and cooling process. After cooling off, the substrate presents a residual compressive stress along the axial direction. Moreover, the substrate deflection can be reduced by improving the initial substrate temperature. This study provided an important reference for optimizing the process parameters in repairing the shaft parts.

The H-class turbine, introduced nearly a decade ago, has reached a significant milestone with its 100th global sale. With 108 units sold and 91 in operation across four continents, accumulating over 3.2 million fired hours, the SGT5-8000H has established itself as a market leader, setting industry benchmarks for performance. Since its launch, the SGT5-8000H's output has increased from 375 MW to 450 MW, and combined cycle efficiency has surpassed 62%. To maintain optimal performance, the platform combustion system (PCS) of the SGT5-8000H has undergone refurbishment in Berlin since 2017. Beginning with a PCS from Samsun, Turkey, the process involves a detailed inspection, repair, recoating, and final assembly. Advanced technologies, such as blue light scanning, enhance efficiency and enable lifecycle assessments. Innovative repair methods, including 3D printed patch repairs using laser powder bed fusion (LPBF), reduce costs. Laser-based cutting and welding automation further minimizes heat input and distortion, ensuring the PCS's reliability and longevity. These technological advancements contribute to the SGT5-8000H's stable and dependable operation.

Recently, laser deposition technologies have made significant advancements in their ability to manufacture high temperature metals and ceramics. One of these technologies, known as Direct Energy Deposition (DED), has the potential to deposit a wide range of materials from polymers to refractory materials, ceramics and functionally graded materials. This study evaluates major microstructural characteristics of WC-Co additively manufactured by DED technology. This material is commonly used for deposition of protective coatings due to its high hardness and excellent wear resistance. To this end, hardness and wear resistance of the DED processed samples were also investigated in this study. WC-Co coatings are generally deposited using various thermal spray technologies. However, it is speculated that DED deposited WC-Co could provide superior properties such as higher hardness and wear resistance. A DED manufactured WC-Co sample was examined by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD). Those studies could provide information about important microstructural features, chemical compositions and phase distribution. All the tests were also repeated on High-Velocity Oxygen Fuel (HVOF) deposited WC-Co with the same composition. Both DED and HVOF produced WC-Co coatings experience decomposition of the carbides into compound phases; however, the DED deposited sample displays unique dendritic and eutectic structures that improve the hardness and wear properties compared to the homogenous HVOF coating. In addition, DED produced samples show higher hardness and relatively better wear resistance compared to the HVOF deposited ones. The obtained results could establish a relationship between microstructural characteristics with hardness and wear properties of both samples.

Spattering is an unavoidable phenomenon in the selective laser melting (SLM) process, which can cause various printing defects and harmful powder recycling. Since the size of powder spattering is too small at the micron level, it is difficult to investigate the entire dynamic spattering process experimentally. The comprehensive understanding of the intricate dynamics of powder spattering during the SLM process remains incomplete. Therefore, we develop a new multiphase flow model to study the transient dynamic behaviors of the gas phase and powder spattering, which agrees well with the experimental observation result. It is the first time that the whole transient dynamic process of powder motion from starting to move induced by the vapor jet to falling to the substrate wall and stopping completely was observed. Powder spattering motion dynamics induced by metal vapor jet and argon gas flow, as a function of time, laser parameters, and location, are presented. The moving speed, total amount, and dropping distribution on the substrate of powder spattering that varies with laser parameters are quantified.

Cobalt chromium (CoCr), a well-known biocompatible material, was additively manufactured using direct energy deposition (DED) technology in this study. Since DED is a relatively new addition to additive manufacturing (AM) processes, there is not enough information about important properties of fabricated parts and components using this technology. This study investigates some important mechanical characteristics of the additively manufactured CoCr using a variety of numerical simulation methods in addition to mechanical tests and experiments. Mechanical experiments such as hardness, wear, and flexural bending test were conducted on DED processed samples. All experiments were also conducted on conventionally processed CoCr specimens for comparison purposes. This study attempts to explain mechanical properties in terms of microstructural characteristics of each sample. DED processed CoCr samples exhibited a complex microstructure with a variety of features such as cellular, columnar, and equiaxed grains within their melt pools. While the DED processed sample had a lower hardness compared to the conventionally processed one, it exhibited a higher wear resistance. These results were discussed in terms of microstructural characteristics and metallurgical bonding knowing that porosity level was negligible in both samples. The out-of-plane mechanical strength of CoCr samples was measured by conducting flexural bending test, and the conventional sample showed a higher flexural modulus than the DED sample. The bend tests were also numerically simulated using two different finite element analysis (FEA) procedures. The FEA results for the DED and conventionally processed samples follow the same trend as the results obtained from the experimental flexural bending test. The layer structure and interfacial bonding of the DED sample could have contributed to the lower flexural modulus compared to the conventional sample.

Cold spray additive manufacturing is an emerging solid-state deposition process that enables large-scale components to be manufactured at high production rates. Control over geometry is important for reducing the development and growth of defects during the 3D build process and improving the final dimensional accuracy and quality of components. To this end, a machine learning approach has recently gained interest in modelling additively manufactured geometry; however, such a data-driven modelling framework lacks the explicit consideration of a depositing surface and domain knowledge in cold spray additive manufacturing. Therefore, this study presents surface-aware data-driven modelling of an overlapping-track profile using a Gaussian Process Regression model. The proposed Gaussian Process modelling framework explicitly incorporated two relevant geometric features (i.e., surface type and polar length from the nozzle exit to the surface) and a widely adopted Gaussian superposing model as prior domain knowledge in the form of an explicit mean function. It was shown that the proposed model is able to provide better predictive performance than the Gaussian superposing model alone and purely data-driven Gaussian Process model, providing consistent overlapping-track profile predictions at all overlapping ratios. By combining accurate prediction of track geometry with toolpath planning, it is anticipated that improved geometric control and product quality can be achieved in cold spray additive manufacturing.

Cold spray (CS) is a solid-state process for depositing metal powder, accelerated by a high-velocity gas such that it bonds to the substrate metal through kinetic impact energy. Although the technology is finding applications in non-load bearing repair and coating applications, work is needed in the quality control procedures for CS for its use in load bearing structural applications. in this study, the viability of electrical conductivity and through thickness ultrasound wave velocity measurement methods are studied to serve as a means for nondestructive quantitative measurement methods for quality control in CS and potentially other additive manufacturing (AM) methods. Eddy current, ultrasound, porosity, hardness, and uniaxial tensile strength tests were conducted on copper and aluminum samples that were manufactured using CS. Ultrasound measurements of longitudinal wave velocity and eddy current electrical conductivity measurements showed good correlation with process conditions that were varied to control particle velocity to intentionally produce samples with varying deposition quality. Influence of process conditions on particle velocity was confirmed via particle image velocimetry. Porosity, hardness, and tensile test results were further correlated to ultrasound wave velocity and electrical conductivity measurements. The results of this work show that nondestructive testing methods can be effectively used to quantitatively assess the cold spray products for quality control purposes.

Cold spray additive manufacturing technology (CSAM) is a progressive method of 3D print of metals and alloys. Its inherent work principles allow production of the components below the material melting points, thereby avoiding several undesired material degradation processes. Among other inherently associated phenomena, the work principles of CSAM involve extreme plastic deformation of the materials, triggering formation of several types of lattice defects. Positron annihilation spectroscopy (PAS) is an analytical technique capable of studying deformation on the atomic scale level, even in extremely deformed materials. In our study, the first historical analysis of CSAM materials by PAS was carried out. For the demonstration, four different base metals were selected (Al, Cu, Ni, Ti). For these, the character of dislocations and vacancies was observed and the respective densities were quantified. The results show that the extremely high strain rate in the cold spray process prevents recovery of vacancies by diffusion to sinks. The deformation-induced vacancies agglomerate into small vacancy clusters. Hence, metals deposited using CSAM contain not only dislocations but also vacancy clusters. Both kinds of defects were detected by positron annihilation spectroscopy.

As an emerging additive manufacturing method, cold spray additive manufacturing (CSAM) has attracted more and more researchers’ attention due to its unique advantages. However, only a few researchers have studied the fabrication of complex structural components. Therefore, it is important to develop a general CSAM framework that is suitable for the fabrication of different shapes of workpieces. In particular, the choice for the optimal kinematic spraying parameters, the prediction of deposit evolution and the planning of spraying trajectory are the most basic and crucial. Different sub-modules are integrated in the proposed framework to solve these problems. In detail, the modeling methodology is used to obtain the optimal kinematic spraying parameters and to predict the deposit evolution in the simulation. Based on the feasible parameters, the trajectory planification methodology is used to generate the spraying trajectory for the workpiece being manufactured, especially the workpiece with complex structure. Finally, the simulation and experimental results of a fabrication for a workpiece with complex structure provide the developed system is reliable and effective. The framework developed in this paper can considered as a general tool for additive manufacturing of with complex structural workpieces in the CSAM.

Developing a cost-effective fabrication method for devices containing metal channels with surface features on the submillimeter scale is essential for the development of novel, high efficiency micro-reactors and heat sinks. Traditional methods are limited by their high cost, low geometric accuracy, high energy consumption, and long processing times. This study presents a low-cost additive manufacturing method using twin wire arc spray to make surface features at the sub-millimeter scale. Water-soluble polyvinyl alcohol (PVA) paste is first placed onto a mold containing a negative of the desired surface features and allowed to cure. The cured PVA is removed from the negative and metal sprayed onto its surface. The deposited metal film was backed by epoxy for added rigidity. The PVA paste was then dissolved in a water bath, resulting in a metal surface with the surface features of the mold. Surface features with length scales as small as 200 μm were reproduced. Coating delamination was prevented by minimizing the temperature of the substrate during spraying by increasing the standoff distance and scanning speed of the spray torch.

High-performance polymers such as poly(ether ether ketone) (PEEK) are appealing for a wide variety of industrial and medical applications due to their excellent mechanical properties. However, these applications are often limited by relatively low thermal stability and conductivity compared to metals. Many methods developed to metallize polymers, including vapor deposition and thermal spray processes, can lead to poor quality control, low deposition rate, and high cost. Thus, cold spray is a promising potential alternative to rapidly and inexpensively produce polymer-metal composites. In this study, we investigated the deposition characteristics of metalpolymer composite feedstock, composed of PEEK powder with varying volume fractions of copper (Cu) flake added, onto a PEEK substrate. We prepared the Cu-PEEK composite powder in varying compositions by two methods: hand-mixing the powders and cryogenically milling the powders. Scanning electron microscopy (SEM) of the feed mixtures shows that cryogenically milling the polymer and metal powders together created uniformly distributed micron-scale domains of Cu on PEEK particle surfaces, and vice versa, as well as consolidating much of the porous Cu flake. In lowpressure cold spray, the relatively large volume fractions of PEEK in the composite mixtures allowed for lower operating temperatures than those commonly used in PEEK metallization (300-500 °C). While the deposition efficiencies of each mixture were relatively similar in single-layer experiments, deposits formed after multiple passes showed significant changes in deposition efficiency and composition in PEEK-rich feedstock mixtures. SEM of deposit surfaces and cross-sections revealed multiple co-dominant mechanisms of deposition, which affect both the porosity and final composition of the deposit. Though present in all samples analyzed, the effects of cryogenic milling were more prevalent at lower Cu concentrations.