A Ni-based powder composed of NiSiB + 60% WC was deposited onto a structural-steel substrate using two methods: laser cladding (LC) and plasma powder transferred arc welding (PPTAW). The resulting surface layers were analyzed and compared. Both methods resulted in the precipitation of secondary WC phases in the solidified matrix, but the PPTAW clad exhibited a dendritic microstructure. The microhardness of the clads prepared by both methods was similar, but the PPTAW clad showed higher resistance to abrasive wear compared to the LC clad. The thickness of the transition zone (TZ) was thin for both methods, with a coarse-grain heat-affected zone (CGHAZ) and peninsula-like macrosegregations observed in clads from both methods. The PPTAW clad showed a unique cellular–dendritic growth solidification (CDGS) and a type-II boundary at the TZ attributed to its thermal cycles. While both methods resulted in metallurgical bonding of the clad to the substrate, the LC method exhibited a lower dilution coefficient. The LC method also resulted in a larger HAZ with higher hardness compared to the HAZ of the PPTAW clad. The findings of this study indicate that both methods are promising for antiwear applications due to their wear-resistant properties and metallurgical bonding to the substrate. The PPTAW clad may be particularly useful in applications that require higher resistance to abrasive wear, while the LC method may be advantageous in applications that require lower dilution and larger HAZ.

The additive manufacturing technique performed via laser powder bed fusion has matured as a technology for manufacturing cemented carbide parts. The parts are built by additive consolidation of thin layers of a WC and Co mixture using a laser, depending on the power and scanning speed, making it possible to create small, complex parts with different geometries. NbC-based cermets, as the main phase, can replace WC-based cemented carbides for some applications. Issues related to the high costs and dependence on imports have made WC and Co powders emerge as critical raw materials. Furthermore, avoiding manufacturing workers’ health problems and occupational diseases is a positive advantage of replacing WC with NbC and alternative binder phases. This work used WC and NbC as the main carbides and three binders: 100% Ni, 100% Co, and 50Ni/50Co wt.%. For the flowability and spreadability of the powders of WC- and NbC-based alloy mixtures in the powder bed with high cohesiveness, it was necessary to build a vibrating container with a pneumatic turbine ranging from 460 to 520 Hz. Concurrently, compaction was promoted by a compacting system. The thin deposition layers of the mixtures were applied uniformly and were well distributed in the powder bed to minimize the defects and cracks during the direct sintering of the samples. The parameters of the L-PBF process varied, with laser scanning speeds from 25 to 125 mm.s^─1 and laser power from 50 to 125 W. Microstructural aspects and the properties obtained are presented and discussed, seeking to establish the relationships between the L-PBF process variables and compare them with the liquid phase sintering technique.

Maintaining high-quality welded connections is crucial in many industries. One of the challenges is assessing the mechanical properties of a joint during its production phase. Currently, in industrial practice, this occurs through NDT (non-destructive testing) conducted after the production process. This article proposes the use of a virtual sensor, which, based on temperature distributions observed on the joint surface during the welding process, allows for the determination of hardness distribution across the cross-section of a joint. Welding trials were conducted with temperature recording, hardness measurements were taken, and then, neural networks with different hyperparameters were tested and evaluated. As a basis for developing a virtual sensor, LSTM networks were utilized, which can be applied to time series prediction, as in the analyzed case of hardness value sequences across the cross-section of a welded joint. Through the analysis of the obtained results, it was determined that the developed virtual sensor can be applied to predict global temperature changes in the weld area, in terms of both its value and geometry changes, with the mean average error being less than 20 HV (mean for model ~35 HV). However, in its current form, predicting local hardness disturbances resulting from process instabilities and defects is not feasible.

The use of parts containing internal channels fabricated by laser powder bed fusion (LPBF) in maraging steel is gaining attention within industry, due to the promising application of the material in molds and forming tools. However, LPBF processing has issues when it comes to unsupported channels, leading to defects that can result in a limited performance and shortened component life. The present study aims to provide a detailed evaluation of the metallurgical effects arising from the LPBF printing of channels made of maraging 300 steel. The results show that channel distortion occurs due to the lack of support, associated with increased roughness at the top part of the channel profile caused by partial melting and loosening of the powder. Statistical analyses showed that distortion is significantly affected by channel length. A high level of porosity derived from a lack of fusion was observed in the region above the channel and was attributed to layer irregularities caused by the absence of support, with a predominance of large and irregular pores. Residual stresses, always of a tensile nature, present a behavior opposed to that of distortion, increasing with increases in length, meaning that higher levels of distortion lead to an enhanced effect of stress accommodation/relief, with porosity having a similar effect. All these phenomena, however, did not seem to affect crystallographic orientation, with a nearly random texture in all cases, most likely due to the energy input used and to an optimized laser scanning strategy. These findings are vital to increase the amount of attention paid towards the design of internal channels, especially with those with the purpose of coolant circulation, since distortions and poor surface finishing can reduce cooling efficiency due to a defective fluid flow, while porosity can have the same effect by hindering heat transfer. Residual stress, in its turn, can decrease the life of the component by facilitating cracking and wear.