Effect of frequency change during pulsed waterjet interaction with stainless steel

Abstract

In the present work a detailed effect of pulsating water jet treatment with the variation of standoff distance on the flat austenitic stainless steel surface has been studied. During the experimentation, at a traverse speed of 30 mm/s accidently the change in frequency was encountered in the repeated test (under same treatment condition) which has been reported in this work. The frequency was changed from f = 20.11 kHz to f = 20.27 kHz during the treatment process at the pressure of p = 70 MPa with variation in standoff distance was increased from z = 5 mm up to z = 101 mm (with step distance of 2 mm between successive standoff distance). The change in microstructural topography of the treated surface under the above-mentioned conditions was observed using scanning electron microscopy (SEM). The strengthening mechanism on the surface and sub-surface region due to the plastic deformation phenomenon caused by the impact of the pulsating jet was evaluated by Vickers microhardness test. The micro hardness test was conducted along the depth of the treated region to analyze the effects in the sub-surface layers. Also, the erosion stages at different standoff distance was evaluated by scanning the surface by optical MicroProf FRT profilometer in order to analyze the nature of erosion phenomenon with the variation of standoff distance and frequency during the treatment process. The results obtained indicates that the change in frequency of the pulsations and the variation in standoff distance has a significant impact on the surface integrity of the treated material. As compare to the untreated surface the hardness of the treated surface was increased up to a certain depth and the higher frequency of pulsations has shown better improvement in the hardness values. The above observations elaborated the effect of an important parameter frequency and standoff distance for better and effective utilization of the technology for the surface treatment application.