**On Defect Minimization Caused by Oxide Phase Formation in Laser Powder Bed Fusion**

**Anna A. Okunkova \*, Semen R. Shekhtman, Alexander S. Metel, Nadegda A. Suhova, Sergey V. Fedorov, Marina A. Volosova and Sergey N. Grigoriev**

> Department of High-Efficiency Processing Technologies, Moscow State University of Technology STANKIN, 127055 Moscow, Russia; s.shekhtman@stankin.ru (S.R.S.); a.metel@stankin.ru (A.S.M.); n.suhova@stankin.ru (N.A.S.); sv.fedorov@stankin.ru (S.V.F.); m.volosova@stankin.ru (M.A.V.); s.grigoriev@stankin.ru (S.N.G.)

**\*** Correspondence: a.okunkova@stankin.ru; Tel.: +7-909-913-12-07

**Abstract:** The article is devoted to the compressive review of the defects observed in the products of the machinery usage made mainly of anti-corrosion steels of the martensite-austenite group, difficult to process materials such as pure titanium, nickel, and their alloys, super and high entropy alloys and triple fusions produced by laser additive manufacturing, particularly the laser powder bed fusion. Studies were conducted on the structural defects observed in such products to improve their quality in the context of residual stress elimination, porosity reduction, and surface roughness improvement. Electrophysical and electrochemical treatment methods of removing oxide phase formation during melting and remelting of deposed tracks in layers are considered (such as ultrasound, plasma, laser, spark treatment, induction cleaning, redox annealing, gas–flame, plasma–beam, plasma–spark treatment). Types of pollution (physical and chemical) and cleaning methods, particularly plasmabased methods for oxide phase removing, are classified. A compressive comparison of low- and high-pressure plasma sources is provided. Special attention is focused on the atmospheric plasma sources based on a dielectric barrier and other discharges as a part of a production setup that presents the critical value of the conducted review in the context of the novelty for transition to the sixth technology paradigm associated with the Kondratieff's waves.

**Keywords:** surface cleaning; laser powder bed fusion; selective laser melting; atmospheric plasma sources; dielectric barrier discharge; nickel alloy; titanium alloy; anticorrosion steel
