Wire and arc additive manufacturing : Opportunities and challenges to control the quality and accuracy of manufactured parts

Wire arc additive manufacturing (WAAM) has been considered as a promising technology for the production of large metallic structures with high deposition rates and low cost. Stainless steels are widely applied due to good mechanical properties and excellent corrosion resistance. This paper reviews the current status of stainless steel WAAM, covering the microstructure, mechanical properties, and defects related to different stainless steels and process parameters. Residual stress and distortion of the WAAM manufactured components are discussed. Specific WAAM techniques, material compositions, process parameters, shielding gas composition, post heat treatments, microstructure, and defects can significantly influence the mechanical properties of WAAM stainless steels. To achieve high quality WAAM stainless steel parts, there is still a strong need to further study the underlying physical metallurgy mechanisms of the WAAM process and post heat treatments to optimize the WAAM and heat treatment parameters and thus control the microstructure. WAAM samples often show considerable anisotropy both in microstructure and mechanical properties. The new in-situ rolling + WAAM process is very effective in reducing the anisotropy, which also can reduce the residual stress and distortion. For future industrial applications, fatigue properties, and corrosion behaviors of WAAMed stainless steels need to be deeply studied in the future. Additionally, further efforts should be made to improve the WAAM process to achieve faster deposition rates and better-quality control.

https://www.mdpi.com/2076-3417/10/5/1563/pdf

Wire arc additive manufacturing of stainless steels: A review

Wire Arc Additive Manufacturing of Hot Work Tool Steel with CMT Process

Study on microstructure and tensile properties of high nitrogen Cr-Mn steel processed by CMT wire and arc additive manufacturing

Thermal modeling and characterization of wire arc additive manufactured duplex stainless steel

Impeller blades are often individual and complex-shaped components made of challenging metals. As the manufacturing of such blades is highly sophisticated, only a few companies worldwide possess the necessary processing knowledge and that is why long production times have to be accepted by customers. To overcome this economic disadvantage, manufacturing technologies are permanent under supervision and it seems that metal additive manufacturing could thereby play an important role in future. In this paper, wire arc additive manufacturing (WAAM) based on gas metal arc welding (GMAW) is considered. Shape-giving GMAW is well known in industrial manufacturing, but its application is limited due to restrictions by the welding process itself: For thinner wall thicknesses, a significant reduction of the weld process energy is required which increases the risk of process instabilities and spatter formation. Extensive welding process-related efforts have been undertaken to overcome this fact and a new GMAW process, called CMT (Cold Metal Transfer) was introduced. CMT is based on a high-frequency forward and backward movement of the welding wire electrode and provides an almost spatter-free and absolute precise, periodic detachment of accurately defined droplets from the filler wire at very low process energies. In combination with an accurate robotic movement of the CMT welding torch, geometries with minimum thicknesses in the range of 2–4 mm can be build up layer by layer. Additionally, a broad range of different, well established and third party-approved GMAW filler metals for joining is available. In this work, an impeller blade-like geometry out of duplex stainless steel has been manufactured by CMT using a filler wire type G 22 9 3 N L. The investigations have shown that the achieved surface roughness is comparable to sand casting and the microstructure is without any evidence for porosity and lack of fusion. Furthermore, an austenite/δ-ferrite weld microstructure with partly preferred grain orientations and a δ-ferrite content of around 30FN exists. The measured mechanical properties, especially strength and toughness, are comparable to data provided by the filler metal data sheet.

Kerstin Chladil

Papers

Material properties of CMT—metal additive manufactured duplex stainless steel blade-like geometries