**1. Introduction**

The UNS S32707 hyper-duplex stainless steel (HDSS) has excellent mechanical properties and corrosion resistance. The pitting resistance equivalent number (PREN = mass% Cr + 3.3 mass% Mo + 16 mass% N) is 49, and the critical pitting temperature (CPT) is 90 ◦C. This material has been widely used in marine engineering equipment [1,2]. The hot working performance of the HDSS is poor due to the high content of Cr, Mo, and N, leading to crack during hot rolling. Nitrogen escapes easily during welding, resulting in the performance of weld metal deteriorates [3,4]. In general, it is di fficult to manufacture a duplex stainless steel, while the selective laser melting (SLM) is an e ffective technique to produce HDSS with the complex shapes. In detail, a higher relative density of duplex stainless steel can be obtained [5], and the precipitation of the σ phase and other harmful phases can be inhibited due to a rapid cooling rate [6].

In recent years, the austenitic stainless steel [7], precipitation hardening stainless steel [8], martensitic stainless steel [9], high manganese steel [10], super-duplex stainless steel (SDSS) [11–14] prepared using SLM were studied. Although SLM technology has a certain basis for the preparation of SDSS, SLM of HDSS with higher nitrogen content has rarely been reported. Shang et al. [15] have shown that the microstructure of UNS S32707 HDSS prepared by SLM from the powder prepared by plasma rotating electrode process (PREP) is mainly ferrite. Although it has high strength and hardness, the ductility and toughness of duplex stainless steel are poor due to the precipitation of nitride at ferrite grain boundary. In this study, the microstructure, mechanical properties and corrosion resistance at di fferent solution annealing temperatures were examined. The objective is to obtain an UNS S32707 HDSS prepared by SLM with balanced austenite-ferrite arrangement, ideal tensile strength, ductility, toughness, and corrosion resistance.
