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

WC-Co hardmetals are widely used in wear-resistant parts, cutting tools, molds, and mining parts, owing to the combination of high hardness and high toughness. WC-Co hardmetal parts are usually produced by casting and powder metallurgy, which cannot manufacture parts with complex geometries and often require post-processing such as machining. Additive manufacturing (AM) technologies are able to fabricate parts with high geometric complexity and reduce post-processing. Therefore, additive manufacturing of WC-Co hardmetals has been widely studied in recent years. In this article, the current status of additive manufacturing of WC-Co hardmetals is reviewed. The advantages and disadvantages of different AM processes used for producing WC-Co parts, including selective laser melting (SLM), selective electron beam melting (SEBM), binder jet additive manufacturing (BJAM), 3D gel-printing (3DGP), and fused filament fabrication (FFF) are discussed. The studies on microstructures, defects, and mechanical properties of WC-Co parts manufactured by different AM processes are reviewed. Finally, the remaining challenges in additive manufacturing of WC-Co hardmetals are pointed out and suggestions on future research are discussed.

/pdf/additive-manufacturing-of-wc-co-hardmetals-a-review-20z4ocs4xw.pdf

Additive manufacturing of WC-Co hardmetals: a review

Additive manufacturing is a process of transforming 3D CAD models into a finished part by adding layers of material. The technology is being used for more than three decades to make prototypes using polymer powders. Over the years, the technique has evolved, which currently allows the industries to manufacture functional parts out of different metals that have high complexity and limited lot size. Tungsten carbide (WC-Co) is a refractory metal with a very high melting point of around 2900 °C and is difficult to manufacture by conventional methods. Hence, tungsten carbide hardmetal parts are made by powder metallurgy technique, wherein tungsten carbide and binder metal powders (cobalt, nickel, iron or alloys of these metals) are pressed into the desired shape and sintered. However, due to the recent advancements, researchers have proven that complex tungsten carbide parts can be made by additive techniques. Hence, the article aims to summarize the three major techniques, Selective Laser Melting (SLM), Selective Laser Sintering (SLS), and Binder Jet 3D printing (BJ3DP) used in the manufacturing of tungsten carbide hardmetal parts. The process variables, metallurgical and mechanical characteristics, and challenges in manufacturing are presented which would serve as a knowledge pool for prospective researchers.

Additive Manufacturing of Tungsten Carbide Hardmetal Parts by Selective Laser Melting (SLM), Selective Laser Sintering (SLS) and Binder Jet 3D Printing (BJ3DP) Techniques

Additive manufacturing (AM) is one of the fastest-growing industrial techniques, bringing many innovative solutions to different manufacturing problems. In AM, a sliced image of the 3D model is layered together to make a 3D object. The main reason for the exponential growth of AM is its numerous advantages over conventional methods, such as high-cost efficiency, less material wastage, a very high degree of freedom, and lesser material constraints. One of the biggest contributors to this growth is the aerospace industry. It is due to the ease of making complex structures and alloys with a very high strength-to-weight ratio (S:W). The authors have comprehensively reviewed the use of AM in the aerospace industry in this review. This review mainly focuses on the metal AM of complex components used in the Aerospace industry. The other topics in this review are an in-depth study of the different AM techniques, a classification of different AM processes, a comparison between conventional and AM techniques, an advantage of AM techniques, and the future scope of AM techniques. The material characterization and microstructure of the components and the different process parameters concerning the cost and irrespective of cost are also briefly discussed. 

A review on metal additive manufacturing for intricately shaped aerospace components

https://link.springer.com/content/pdf/10.1007/s43452-021-00306-3.pdf

Effect of shot peening on the surface properties, corrosion and wear performance of 17-4PH steel produced by DMLS additive manufacturing

Martensitic stainless steels are widely used in industries due to their high strength and good corrosion resistance performance. Precipitation-hardened (PH) martensitic stainless steels feature very high strength compared with other stainless steels, around 3-4 times the strength of austenitic stainless steels such as 304 and 316. However, the poor workability due to the high strength and hardness induced by precipitation hardening limits the extensive utilization of PH stainless steels as structural components of complex shapes. Laser powder bed fusion (L-PBF) is an attractive additive manufacturing technology, which not only exhibits the advantages of producing complex and precise parts with a short lead time, but also avoids or reduces the subsequent machining process. In this review, the microstructures of martensitic stainless steels in the as-built state, as well as the effects of process parameters, building atmosphere, and heat treatments on the microstructures, are reviewed. Then, the characteristics of defects in the as-built state and the causes are specifically analyzed. Afterward, the effect of process parameters and heat treatment conditions on mechanical properties are summarized and reviewed. Finally, the remaining issues and suggestions on future research on L-PBF of martensitic precipitation-hardened stainless steels are put forward.

Xin Tong

Papers

Laser Powder Bed Fusion of Precipitation-Hardened Martensitic Stainless Steels: A Review