Abstract
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.
Highlights
Precipitation-hardened (PH) stainless steels were invented to meet the demand of the rapid development of the aerospace industry since the 1940s [1,2]
(1040 ◦ C for 30 min) and quenched prior to the subsequent aging; 3 SHT was conducted at 788 ◦ C for 2 h followed by water quenching to room temperature; 4 Aging was conducted at 482 ◦ C for 1 h followed by water quenching to room temperature
Few studies tested the performance of Laser powder bed fusion (L-PBF) fabricated 17–4 PH stainless-steel parts under cyclic loading, and the results indicated that fatigue properties were more sensitive to the defects generated by L-PBF, leading to the low fracture strains and stresses under cyclic loading
Summary
PH stainless steels are widely used in the aerospace industry [11,12], the marine industry [13], nuclear reactor components [14], chemical process equipment [15], and medical apparatus due to their high tensile strength, impact strength, fracture toughness, and corrosion resistance at typical service temperatures below 300 ◦ C [15,16]. Most of these parts are important load-bearing components of heavy machinery in a demanding service environment. Previous investigations on phase transformation behaviors, as well as the effect of process parameters and post-heat treatments on mechanical properties, are summarized and reviewed
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