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Title: Studies on Slurry Erosion of Hard Protective Coatings on 13-4 Martensitic Stainless Steel for Hydro Turbine Blades
Authors: Nath, Gaurav
Supervisor: Kumar, Satish
Keywords: Slurry erosion;13-4 martensitic stainless steel;HVOF coating;Boronizing;DPM Modeling
Issue Date: 29-Jun-2017
Publisher: MED
Abstract: Silt erosion is a tenacious hurdle in the efficient operation of hydroelectric plants. The costs involved in repairing the damage done by silt erosion as well as the reduced power output is not favourable. Solution to this problem lies in the use of protective coatings which have proven to be quite effective against silt erosion. Furthermore, predicting the erosion affected areas beforehand using simulations also help to combat silt erosion. The main aim of this study was to evaluate the slurry erosion resistance of the hard protective coatings used on hydro turbine blades to minimize the damage done by silt erosion. The protective coatings chosen for this study were high velocity oxygen fuel (HVOF) applied 86WC10Co4Cr cermet and boronizing. The most commonly used turbine blade steel 13Cr4Ni martensitic stainless steel (13-4 MSS) was chosen as the substrate for the coatings. An improvement upon the existing 86WC10Co4Cr cermet has also been made by the addition of 2 wt% yttrium oxide (Y2O3) into the cermet. A comparative study of the slurry erosion resistance of 13-4 MSS, 86WC10Co4Cr cermet, Y2O3 added 86WC10Co4Cr cermet and boronized 13-4 MSS substrate has been made. A slurry pot tester with an abrasive slurry (10 wt% silica sand in water) was used for the wear testing. Coating characterization was done using SEM, EDS and XRD. Hardness and surface roughness of the coatings were also determined. It was found from the study that coated steels exhibited higher wear resistance as compared to the bare steel. Addition of Y2O3 also led to an increase in wear resistance over the conventional cermet. Boronized 13-4 MSS was found to have the highest wear resistance. A CFD simulation has also been done to model the phenomenon of silt erosion in a Pelton turbine nozzle and spear arrangement and Pelton turbine runner. The simulation was done in ANSYS FLUENT using discrete phase modelling (DPM). The eroded areas predicted by simulation were found to be in agreement with the literature and field results. The effect of inlet parameters on the erosion rate was also found to be in agreement with the literature.
Description: ME THESIS
Appears in Collections:Masters Theses@MED

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