Autor(s) Krawczyk, Janusz
Autor(s) Jasionowski, Robert
Date of issue 2018
ISSN 1733-8670 pl_PL
Abstract The cavitation is a one of the most wear mechanism which is related to the liquid flow. It is one of the most destructible for the stainless materials. The local changes in the pressure of the liquid stream related to the flow along the metal component cause the straightening of the surface area, its erosion and formation of the pits at the surface layer. The cavitation erosion value is related to the material microstructure, geometry of the element, the phase composition of the material and the surface roughness. In the present paper the investigation of the cavitation process for the duplex stainless steel was performed. At the beginning the rounded samples from the duplex stainless steel with the diameter of 2cm and 1 cm high were grinded and polished to obtain the similar properties of the material surface. The each of the small changes could effect at the results of the tests. Further the cavitation test were performed by the use of the jet – stricking device with the controlled parameters of the ;liquid flow. The tests were performed through the 5, 15, 30, 60, 120, 300 min. Further the microscopic investigations of samples surfaces were performed. The LM and SEM analysis allow to describe all changes at the material surface, as a result of the cavitation. Additionally the X-Ray diffraction analysis were performed. It allow to occur the information about the changes of the austenite volume fraction as a consequence of the mechanical destabilization of the austenite. The changes of the weight for the investigated materials was not significant, the changes of the samples mass was observed after the 30min. After that time the constant increase of the weight loss was observed. But the cavitation is a mechanism of the wear in a significant way influent at the material surface not for the mass of the material. Changes of the austenite volume fractions for the first samples are equal to the standard error of measurement. Than after the 60 min changes of the austenite volume fraction increase with the time. The same tendency was observed in the case of the hardness measurements. At the beginning the changes was not significant. But for the long experiment time the hardness increase is well visible. Also the cavitation results is a cracking along the interphase boundaries, which could resulted in the chipping of the material volume. One of the most important results were a description of changes of the mechanisms of wear and its intensity thorough the time. First of the mechanisms is a plastic deformation of the material surface. Results of the plastic deformation significant increases and after some time stabile at the same level. The next stage of the cavitation was erosion and next the interphase decohesion. This two effects increases simultaneously. The last of the mechanism is mechanical destabilization of the austenite, but the clear results of the mechanical destabilization of austenite was observed only for the last sample. Martensite transformation of the material could change the material mechanical properties but for the stainless steels could resulted in the electrochemical corrosion of such material, especially through the formation of electrochemical potential between the austenite and martensite.
Publisher #
Title The effect of cavitation erosion on austenitic-ferritic material
Type Journal Article en_US