Sediment Erosion Behavior of WC-Co-Cr Coatings on 13-4 Martensitic Stainless Steel for Hydraulic Turbine Application

Abstract

Hydraulic turbines are subjected to erosion due to suspended sediments, which diminishes their performance and service life. The present study has been carried out to study the sediment erosion behavior of WC-10Co-4.4Cr coatings on 13Cr-4Ni martensitic stainless steel for velocities varying in the range of 14.5–32.5 m/s of medium-specific speed Francis turbines. Experiments were conducted in a pot tester at different orientation angles in the range of 15–90 deg, sediment concentration in the range of 7000–11,000 PPM, and sediment particle size between 90.5 to 362.5 μm. The particles are collected from the Bhilangana-III hydroelectric power plant. Erosion rate was determined from the average of the material loss of the two samples used in a test, and each test was performed three times to check the repeatability. The erosion rate is increased with impact velocity and particle size but slightly decreased with the sediment concentration. The power index value of the velocity is decreased with increasing orientation angle. Scanning electron microscopy revealed combined ductile–brittle erosion at acute angles and brittle erosion at oblique angles (≥45 deg). An empirical correlation, as a contribution of deformation and cutting wear, was developed to determine the total erosion rate, which showed an accuracy of ±15% for the experimental data. The correlation is primarily useful for numerical modeling of erosion wear due to suspended solids in water.