Evaluation of thermal and geometric properties of martensitic stainless steel thin walls built by additive manufacturing cold metal transfer (CMT) processes

Cold metal transfer wire arc additive manufacturing (CMT-WAAM) has attracted attention in recent years due to its ability to print walls with higher dimensional accuracy than regular WAAM. To print near net shape parts by CMT-WAAM, there is a need to define a set of height-related geometrical parameters (HGPs) that can capture, quantify, and compare the quality of the height of the produced parts. In the presenting study a set of HGPs, namely, the average height error (AHE), maximum height variation (MHV), and average absolute slope (AAS) are defined and assessed. Fifteen single-track multi-layer walls are printed to check the effect of process parameters on the defined HGPs. It is found that the stability and quality of the print cannot be guaranteed by checking the visual appearance of the single beads and at least five-to-ten-layer walls should be printed. It is also found that the travel speed (TS) and wire feed speed (WFS) have positive monotonic relationships with AAS and MHV, respectively. Correlations between process parameters and HGPs are modeled and optimized using multi-objective optimization and a validation test is performed to check the validity of the developed models. Moreover, HGPs of walls printed using unidirectional and bidirectional path strategies are calculated and compared. Defined HGPs

Section: Bead Height Referencesmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Modeling and optimization of height-related geometrical parameters for thin wall structures manufactured by metal additive manufacturing

Dehaghani,

Tang,

Panicker

et al. 2023

Knowledge-based manufacturability assessment for optimization of additive manufacturing processes based on automated feature recognition from CAD models

Stavropoulos

Tzimanis

Souflas

et al. 2022

Additive manufacturing (AM) is a significant development of the manufacturing sector that has emerged during the last decades and tends to change the way products are designed, manufactured, and repaired, enabling unprecedented flexibility levels. The unique process mechanism of AM enables the realization of complex designs after considering design limitations, which are unique to each process mechanism and machine. These limitations, together with the lack of established AM-related knowledge, lead to the design of parts that are not fully conforming with AM buildability restrictions, resulting in failed builds. To this end, this work presents a methodology that enables to embed the AM-related knowledge and use it for an automated manufacturability assessment. The 3D model of a part is used as an input in an.stp format, and the features that are relevant for AM manufacturability are recognized from the global CAD. Then, an analysis of the manufacturability of these features according to the limitations of the process and/or machine is performed, and design changes are suggested to the user aiming to improve the process outputs. The whole methodology is implemented in a software tool with an intuitive user-interface that supports the users in the design of parts that will be made with additive manufacturing.

Characterization of cold metal transfer and conventional short-circuit gas metal arc welding processes for depositing tungsten carbide-reinforced metal matrix composite overlays

Karimi

Wang

Jelovica

2023

This paper compares the processing characteristics of advanced CMT (cold metal transfer) and conventional GMAW-S (gas metal arc welding with short-circuit metal transfer) processes for depositing Ni-WC MMC (nickel-based metal matrix composites reinforced with WC) overlays. In contrast to common expectations, advanced CMT technology with mechanically assisted droplet transfer could not demonstrate significant advantages over the GMAW-S process; on the contrary, CMT exhibits marginal disadvantages in terms of carbide transfer efficiency, volume fraction of retained WC, and deposition rate. Some carbides originally contained in the core of the feed wire are blown away and expelled out of the processing zone leading to physical losses of WC particles during the deposition processes, which is more significant for the CMT process owing to much higher waveform cycle frequency and cyclic feed wire retractions. CMT exhibits superior waveform stability, better control over penetration depth, marginally lower dilution level, and exceptional arc stability. The main parameters affecting carbide transfer efficiency and volume fraction of retained WC are wire feed speed and travel speed for both processes; increased wire feed speed and travel speed generally lead to decreased carbide transfer efficiency and reduced volume fraction of retained WC. Shielding gas may have different effects on the outcomes for the CMT and GMAW-S processes. CMT overlays show comparatively higher W and lower Fe concentration in the matrix, while GMAW-S overlays show a higher concentration of Fe in the matrix (due to elevated dilution level) with marginally higher matrix microhardness and more herringbone-like secondary carbide precipitates.