Rapid solidification of martensitic stainless steel atomized droplets

Abstract

The microstructure of martensitic stainless steel powders produced by inert gas atomization was investigated. Depending upon the powder particle size, the microstructure was found to exhibit a cellular, dendritic, or martensitic morphology. Relationships between the microstructure scale and the particle diameter were identified. It was found that at a critical particle diameter of 25 to 30 m, the structure changed from cellular/dendritic (96.5 vol pct bcc and 3.5 vol pct fcc) to martensite. The solidification path of the powder particles below and above 25 to 30 m in size was considered. High-temperature X-ray diffraction (HTXRD) measurements revealed that there is a delay in the appearance of the fcc phase for the small particle size. The delay in the appearance of the fcc phase is a result of different nucleation sites for the fcc phase between the large and the small particle size.

Electrochemical Behavior, Microstructure, and Surface Chemistry of Thermal-Sprayed Stainless-Steel Coatings

“…These elements added in small quantities are strong carbide formers and prevent the onset of chromium carbide precipitation and hence, intergranular corrosion [29][30][31]. Such Ti-or Nb-rich precipitates were not observed in the coatings nor in the arc melted feedstock which may be explained by a combination of two factors: (i) the relatively high cooling rates in the atomization process (10 3 -10 6 • C/s [32]) and (ii) the low wt.% addition of both elements in the steel formulation. The rapid solidification of the metal implies very little time for Ti and Nb atoms to combine with the carbon and form the precipitates.…”

Modelling of delta ferrite to austenite phase transformation kinetics in martensitic steels: Application to rapid cooling in additive manufacturing

“…It is interesting to note that the microstructure is changing with the powder size: small particles are ferritic (Figure 7 Such microstructure changes in steel powders are not particularly common in the literature. However, in 2002, Pryds and Pedersen [33] observed this phenomenon in a martensitic powder of X20 CrMoV 12-1 steel. To explain this result, the authors estimated the cooling rate of the powder particles as a function of their size.…”

Analysis of Stainless Steel Waste Products Generated during Laser Cutting in Nitrogen Atmosphere

“…Heterogeneous nucleation is probable to occur during the solidification flight of fine particles owing to numerous collisions experienced by the fine particles. The growth of a dendrite across the whole particles is thus possible due to the high degree of supercooling occurring in the fine particles [15,16]. After that stage, the particles cool down, which can be likened to quenching.…”