Surface characterisation of fine inert gas and water atomised stainless steel 316L powders: formation of thermodynamically unstable surface oxide phases

Abstract

New insights are presented on the speciation of surface oxide phases on fine inert gas atomised (GA, ,45 and ,4 mm) and water atomised (WA, ,45 mm) stainless steel AISI 316L powders. Xray photoelectron and Auger electron spectroscopy, scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry were applied for the characterisation. Oxidised manganese was strongly enriched in the outermost surface oxide of the GA powders (13 and 47 wt-%), an effect increasing with reduced particle size. Manganese and sulphur were enriched in oxide nanoparticles on the surface. Oxidised silicon (59 wt-%) was enriched on the WA powder surface. Tri-or tetravalent manganese oxides were observed on the GA particles in addition to a-Fe 2 O 3 , and Cr 2 O 3 . The oxide of the WA powder revealed in addition the likely presence of a silicate rich phase, mainly consisting of tetravalent Si, di-and/or trivalent Fe, and hexavalent Cr, which was confirmed not present as chromate.

Metal release from stainless steel in biological environments: A review

“…A series of studies on gas-and water-atomized AISI 316L stainless steel powder particles of different size (<45 and <4 lm) showed the importance of the route of manufacture and the cooling rate for their physical properties such as magnetic properties and crystallographic microstructure, 146 electrochemical properties (ennoblement), 29 surface oxide characteristics (composition, phases, phase distribution, inclusions, and crystallinity), 29,147 corrosion resistance, 29,148 and metal release into different solutions. 24,29,71,78,79,92 The particles, especially the smallest ones, were despite similar bulk composition very different in all these properties compared with corresponding massive sheet of the same stainless steel grade.…”

“…146,[149][150][151][152][153] The presence of water vapor or oxygen during solidification also strongly influences the oxide composition and alloy microstructure. 29,147,154 Similar factors influence other kind of particles generated, e.g., during welding, particles that are very different in composition, microstructure, and solubility, compared with particles (independent of size) and sheet of stainless steel. 155 Heat treatments applied in vacuum, air, or argon, and cooling (furnace or water-cooled) of orthodontic wires of unreported composition or grade have been shown to increase the release of Ni into artificial saliva compared with non-heat-treated control surfaces, and to result in substantial (greater than tenfold) differences in Ni release depending on treatment.…”

Effect of atomization on surface oxide composition in 316L stainless steel powders for additive manufacturing

“…The relative presence of tetravalent Si would increase as a function of the decreasing partial pressure of oxygen in the atomizing atmosphere and with increasing cooling rate of the metal particles in case of water‐atomizing. A recent study 18 that compared gas‐atomized to water‐atomized powders provided similar observations; no Si oxide was found on a gas‐atomized powder, whereas Mn together with Fe and Cr formed the surface oxide instead. Additionally, the content of Mn in the surface oxide layer on the gas‐atomized powder was found to increase as the powder particle size decreased, in line with the observations by Norell and Nyborg for a gas‐atomized 12% Cr‐steel powder 14 .…”

Identification of chemical form of stable carbon released from type 304L and 316L stainless-steel powders in alkaline and acidic solutions under low-oxygen conditions

“…The oxide thickness was estimated to be approximately 4 nm for both powders from half the decay of the oxygen content. The oxide layers are mainly composed of Si, which implies that these powders are water-atomized stainless-steel powders (Klar and Samal 2007;Hedberg et al 2012Hedberg et al , 2013, meaning that the stainless-steel powders used in this study were produced by a water atomization process. The process essentially consists of the atomization of a stream of liquid metal by high-pressure water jets (Dunkley 1978).…”

“…In other words, it is important to know whether or not the composition of the oxide layer affects the chemical form of the carbon. For example, the stainless-steel powders produced by the gas atomization process have an iron, chromium and nickel oxide layer (Hedberg et al 2012(Hedberg et al , 2013. Comparing the data on the chemical form of carbon released from water-atomized and gas-atomized powders with different oxide compositions could help clarify the effect of the oxide composition on the chemical form of carbon.…”