Normalizing Effect of Heat Treatment Processing on 17-4 PH Stainless Steel Manufactured by Powder Bed Fusion

• Published in: Metals (Basel ) Vol. 12; no. 5; p. 704
• Main Authors: Yeon, Si-Mo, Yoon, Jongcheon, Kim, Tae Bum, Lee, Seung Ho, Jun, Tea-Sung, Son, Yong, Choi, Kyunsuk
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.05.2022
• Subjects: 17-4 PH stainless steel; Additive manufacturing; Aging; Corrosion resistance; Delta ferrite; Elongation; Grain size; Grains; Heat treating; Heat treatment; laser powder bed fusion; Lasers; Martensite; Martensitic stainless steels; Mechanical properties; Microstructure; Nitrogen; Normalizing (heat treatment); Powder beds; Precipitates; Precipitation hardening steels; Retained austenite; Scanning electron microscopy; selective laser melting; Stainless steel; Steel making; Tensile strength; Yield stress; United States > US; Japan
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met12050704

Laser powder bed fusion (L-PBF)-processed 17-4 PH stainless steel (SS) generally exhibits a non-equilibrium microstructure consisting mostly of columnar δ-ferrite grains and a substantial fraction of retained austenite and martensite, contrary to 17-4 PH SS wrought with a fully martensite structure and coarse grains. Despite the different microstructures of L-PBF and wrought 17-4 PH SS, post-processing is typically performed using the conventional heat treatment method. The insufficient effect of the heat treatment on the L-PBF product produces a δ-ferrite phase in the microstructure. To obtain improved mechanical properties, the addition of a normalizing treatment to the conventional heat treatment after L-PBF in a nitrogen gas environment was investigated. The fully martensitic matrix developed by adding the normalizing treatment contained homogeneous Cu precipitates and exhibited a similar or improved strength and elongation to failure compared to the wrought SS.