Influence of mechanical properties of tungsten carbide–cobalt thermal spray coatings on their solid particle erosion behaviour

The present investigation has been carried out in order to study the erosion wear behaviour of WC-Co base thermal spray coatings. WC-12Co and WC-10Co-4Cr coatings were deposited by means of high velocity oxygen fuel (HVOF) thermal spraying. The erosion tests were conducted at impact angles of 30 and 90u using SiC particles of ~50 mm in diameter as erodent, at a velocity of 83.4 m s -1. It has been found that the erosion rate for both coated systems was higher when the test was carried out at an angle of 90°. The through-thickness residual stresses of the coatings, as well as the microstructural characterisation, allowed an explanation of the results and the erosion mechanisms in each case. It has been found that, under the experimental conditions carried out in the present study, the WC-10Co-4Cr coating exhibited a higher erosive wear resistance as compared to the WC-12Co coating. © 2012 Institute of Materials, Minerals and Mining

Friction Correction of Austenite Flow Stress Curves Determined under Axisymmetric Compression Conditions

The experimental flow stress curves of structural steels obtained from axisymmetric compression tests conducted under hot-working conditions very often include the frictional effects present at the tool/specimen interface. Such effects have a significant influence on the flow stress and therefore, should be corrected prior to any quantitative analysis aimed at determining the constitutive description of these materials. Commonly, such a correction is carried out by assuming a constant friction coefficient (μ) or friction factor (m) independent of deformation conditions, which is an unrealistic approach. The present investigation analyzes experimentally the frictional effects that occur when steel is deformed under axisymmetric compression conditions in the temperature range of 850 to 1200 °C at a strain rate of 0.1 s−1 and applied effective strains of 1, employing cylindrical samples with an initial diameter to initial height ratio (d0/h0) in the range of 0.5 to 2. Finite element modeling (FEM), as well as element-free Galerkin modeling (EFGM), have been employed for the analysis and prediction of the von Mises stress distribution, barreling and amount of metal folding undergone by the compression specimens. It has been shown that the increase in flow stress due to frictional effects can be corrected on the basis of either μ or m, by assuming that these parameters vary in the course of plastic deformation and are strongly dependent on deformation temperature. A novel procedure for the systematic correction of the flow stress curves, taking into consideration the changes in friction conditions during plastic deformation, has been proposed.Fil: Puchi-Cabrera, E. S.. Universite Des Sciences Et Technologies de Lille; Francia. Universidad Central de Venezuela; VenezuelaFil: Guérin, J. D.. Universite Des Sciences Et Technologies de Lille; FranciaFil: La Barbera-Sosa, J. G.. Universite Des Sciences Et Technologies de Lille; Francia. Universidad Central de Venezuela; VenezuelaFil: Álvarez Hostos, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; ArgentinaFil: Moreau, P.. Universite Des Sciences Et Technologies de Lille; FranciaFil: Dubar, M.. Universite Des Sciences Et Technologies de Lille; FranciaFil: Dubar, L.. Universite Des Sciences Et Technologies de Lille; Franci