Wear rates and specific energies of some ceramic, cermet and metallic coatings determined in the Coriolis erosion tester

A series of ceramic, cermet and metallic coatings of known resistance to slurry jet erosion has been subjected to sliding bed wear using a 10 wt.% aqueous slurry of 80 grit crushed alumina particles in the Coriolis erosion tester. Wear scar cross-sections have been measured and specific energies for material removal calculated for these coatings as well as for some bulk solid materials for reference purposes. Thermal-sprayed coatings included high velocity oxygen-fuel (HVOF)-sprayed WC-12Co, Cr3C2/NiCr and 316L steel, plasma-sprayed (PS) Al2O3 and Al2O3/TiO2 and are-sprayed 440C steel. Pulsed laser clad coatings of two FeCrB based alloys were also tested. The Coriolis erosion tester consists of a 150 mm diameter rotor with a diametral passage in which a flat plate specimen is located on each side, equidistant from the rotation centre. Slurry, delivered to a central orifice, is constrained to flow outwards through the channel as the rotor is turned at speeds up to 7000 rpm, the erodent particles being pressed onto the test specimen surface by the Coriolis force. The cross-sectional area of the scar is measured as a function of distance from the rotation centre and, through a summation of an expression for frictional work done, a value for the specific energy for material removal (essentially a measure of erosion resistance) is calculated. The test method seeks to simulate the wear environment in slurry pumps and cyclones in which particles move rapidly over the test surface either singly or in a bed. The wear rate of a WC-Co cermet was found to be similar to 1000 times lower than that of 316L stainless steel. The remarkable ability of the Coriolis erosion tester to discriminate in the erosion performance of different materials is discussed in terms of particle trajectories and the probable wear mechanism. Coriolis test results are compared with those for slurry jet erosion and the applicability of the two tests for erosion resistance ranking of hard coating materials is discussed. (C) 1999 Published by Elsevier Science S.A. All rights reserved.