Water droplet erosion assessment in the initial stages on AISI 316 L using kernel average misorientation

journal article in Web of Science

en

Surfaces exposed to natural forces in the form of water droplets are structurally deformed over time through changes in their surface morphology. Plastic deformation in thin subsurface layers where compressive stress prevails is typical for this stage of erosion. The stress accumulation does not exceed the fatigue limit, so the structural integrity is not broken. Information about this stage has been obtained by post-experimental assessments using various observation techniques. This article considers the changes to a surface using techniques to assess a specific site before and after exposure to the erosive action of water droplets. An electron backscatter diffraction analysis was conducted pre-exposure of water droplets for detection on an electrochemically polished surface of stainless steel AISI 316 L. Specific areas that were exposed to the effects of water droplets at subsonic speed were marked with indents. The droplets were generated by an ultrasonic pulsating water jet (PWJ) with a nominal frequency of 40 kHz and supply pressure of p = 50 MPa. To assess the development in the very early stages of erosion, individual runs were performed with a time range of 1-3 s. The erosion development was compared with control runs, where a continuous water jet (CWJ) with a frequency of 1 Hz was used with a time range of 3-6 s. A post-exposure electron backscatter diffraction analysis showed a real change in the grain orientation using kernel average misorientation. It was found that multiple droplet impingement changes the grain geometry and results in an increase in misorientation inside the grains. The misorientation distribution in the zone treated by the water jet was not homogeneous over the entire cross-section of the sample; the CWJ required double or even triple the time to achieve a similar level of plastic deformation when compared to the PWJ.

Surfaces exposed to natural forces in the form of water droplets are structurally deformed over time through changes in their surface morphology. Plastic deformation in thin subsurface layers where compressive stress prevails is typical for this stage of erosion. The stress accumulation does not exceed the fatigue limit, so the structural integrity is not broken. Information about this stage has been obtained by post-experimental assessments using various observation techniques. This article considers the changes to a surface using techniques to assess a specific site before and after exposure to the erosive action of water droplets. An electron backscatter diffraction analysis was conducted pre-exposure of water droplets for detection on an electrochemically polished surface of stainless steel AISI 316 L. Specific areas that were exposed to the effects of water droplets at subsonic speed were marked with indents. The droplets were generated by an ultrasonic pulsating water jet (PWJ) with a nominal frequency of 40 kHz and supply pressure of p = 50 MPa. To assess the development in the very early stages of erosion, individual runs were performed with a time range of 1-3 s. The erosion development was compared with control runs, where a continuous water jet (CWJ) with a frequency of 1 Hz was used with a time range of 3-6 s. A post-exposure electron backscatter diffraction analysis showed a real change in the grain orientation using kernel average misorientation. It was found that multiple droplet impingement changes the grain geometry and results in an increase in misorientation inside the grains. The misorientation distribution in the zone treated by the water jet was not homogeneous over the entire cross-section of the sample; the CWJ required double or even triple the time to achieve a similar level of plastic deformation when compared to the PWJ.

Erosion; EBSD; Incubation stage; Droplet impingement; Misorientation; KAM

01.03.2024

ELSEVIER SCI LTD

London

1879-2464

191

March

1–14

14