Changes of stainless steels surface morphology as a result of interaction with intense pulsed plasma beams containing ions of rare earth elements
Stainless steels are used in numerous industrial applications, mainly due to their excellent corrosion resistance. However, in many cases their low hardness and poor tribological properties impose strong limitations. On the other hand, there are many examples that require the use of electrolyte corrosion and high temperature corrosion resistant materials, which at the same time exhibit good wear resistance. Examples of such applications include liquid flow sensors, temperature, pressure and humidity sensors for aggressive environments, interconnectors for solid oxide fuel cells (SOFC) etc. In all these cases stainless steels are frequently used. The beneficial effect of active elements with high oxygen affinity, such as yttrium, cerium, lanthanum and other rare earth elements (REE) on high temperature oxidation resistance and corrosion resistance against aggressive media has already been studied, e.g. [1, 2]. In addition, these elements added to the bulk alloys or to their surfaces dramatically improve the oxide scale adherence [4]. On the other hand, it is known from our recent study that the surface modification process using intense plasma pulsed leads to improvement of the tribological properties of unalloyed steels [5–7]. Pulsed-plasma treatment – a procedure developed at the Soltan Institute for Nuclear Studies (SINS) Świerk, Poland, consists in treating a solid with plasma pulses of Changes of stainless steels surface morphology as a result of interaction with intense pulsed plasma beams containing ions of rare earth elements Bozena Sartowska, Jerzy Piekoszewski, Lech Waliś, Elzbieta Skladnik-Sadowska, Marek Barlak
Effect of yttrium and erbium ion implantation on the oxidation behaviour of the AISI 304 austenitic steel
Abstract The beneficial effect of the addition of yttrium and erbium by ion implantation on the oxidation behaviour of AISI 304 stainless steel at 1173 K has been investigated. Isothermal oxidation tests have been conducted for up to 500 h. The effect of ‘rare earth elements’ (REE) have been studied previously in order to enhance the oxidation behaviour of different alloys. The results show that yttrium and erbium have similar effects, reducing the rate of continuing scale growth and inhibiting scale failure processes. It is concluded in this study, that both reactive elements inhibit the growth of the poorly protective and adherent oxides rich in iron and chromium, which help the spalled behaviour, together with a smaller oxide grain size.
Properties of a monopivot centrifugal blood pump manufactured by 3D printing
An impeller the same geometry as the impeller of a commercial monopivot cardiopulmonary bypass pump was manufactured using 3D printing. The 3D-printed impeller was integrated into the pump casing of the commercially available pump to form a 3D-printed pump model. The surface roughness of the impeller, the hydraulic performance, the axial displacement of the rotating impeller, and the hemolytic properties of the 3D-printed model were measured and compared with those of the commercially available model. Although the surface roughness of the 3D-printed model was significantly larger than that of the commercially available model, the hydraulic performance of the two models almost coincided. The hemolysis level of the 3D-printed model roughly coincided with that of the commercially available model under low-pressure head conditions, but increased greatly under high-pressure head conditions, as a result of the narrow gap between the rotating impeller and the pump casing. The gap became narrow under high-pressure head conditions, because the axial thrust applied to the impeller increased with increasing impeller rotational speed. Moreover, the axial displacement of the rotating impeller was twice that of the commercially available model, confirming that the elastic deformation of the 3D-printed impeller was larger than that of the commercially available impeller. These results suggest that trial models manufactured by 3D printing can reproduce the hydraulic performance of the commercial product. However, both the surface roughness and the deformation of the trial models must be considered to precisely evaluate the hemolytic properties of the model.