Erosion-corrosion behaviour of Zirconia WC-6Co, WC-6Ni and SS316

The current study investigates a ceramic, two cermets and a metal under solid-liquid impingement with 3.5% NaCl and 150mg/l hydraulic fracturing sand at two extreme angles of impact, 90° and 20°. The materials tested were Zirconia, sintered WC-6Co, sintered WC-6Ni and SS316. Each material was exposed to a testing regime using re-circulating impinging jet apparatus with a velocity of 19m/s and one hour duration. The electrochemical properties of the materials were investigated in-situ through anodic and cathodic polarisation and application of cathodic protection. Post experimental analysis of the degraded surface was completed using Scanning Electron Microscopy (SEM) and Optical 3D Imaging. Zirconia exhibited a brittle response to erosion-corrosion testing with the mass loss at 90° being fifty times greater than the negligible mass loss at 20°. WC-6Co and WC-6Ni both outperformed SS316 under all solid-liquid impingement erosion-corrosion testing regimes. WC-6Ni exhibited slightly better erosion-corrosion resistance over WC-6Co at both 90° and 20°. SS316 had the best corrosion resistance and showed passivation during anodic polarisations in solid-liquid impingement conditions. The nickel binder increased the corrosion resistance of WC-6Ni over WC-6Co. Cathodic protection was successfully applied on sintered WC-6Co and SS316 isolating the key components of erosion-corrosion

Influence of metallic matrix on erosion-corrosion behaviour of high chromium cast irons under slurry impingement conditions

Chromium cast irons (CCI) comprise versatile materials that encompass a range of compositions and microstructures often chosen to promote good wear resistance. There are, however, issues that arise when the cast iron is required to operate in conditions where corrosion, as well as, wear is a factor. This scenario usually results in adapting the composition of the CCI in order to achieve higher chromium content in the metallic matrix and, thereby, to attain the corrosion resistance exhibited by high-Cr stainless steels. This paper comprises a comparison of the corrosive wear behaviour of an austenitic-based hypoeutectic cast iron and a martensitic-based, near-eutectic cast iron with the associated stainless steels, in a saline water under solid-liquid submerged jet conditions. A comprehensive experimental methodology has been adopted including evaluation of the behaviour of the materials in free erosion-corrosion conditions and with the application of cathodic protection. This approach has extended the understanding of the fundamental deterioration mechanisms in different hydrodynamic conditions and has highlighted the complexities of the mechanical/electrochemical interactions occurring during erosion-corrosion. An important feature is the influence of micro-galvanic interactions at phase boundaries. The impact of the findings has been discussed in terms of CCI alloy selection and corrosion control strategies

Effect of impact angle on the slurry erosion-corrosion of Stellite 6 and SS316

This study is an investigation of the effect of impingement angle on slurry erosion-corrosion of Stellite 6 manufactured by sand casting, lost wax casting and SS316. The tests were performed using an impingement rig in which a slurry with 3.5% NaCl and 1.177g/l suspended angular sand particles at 19m/s were recirculated for one hour. The results were obtained for angles of 20°, 45°, 60° and 90° to the exposed surface. Post experimental analysis using light microscopy, surface profiling and SEM assisted with clarification of the wear mechanisms and assessment of the severity of surface damage. Stellite 6 consistently exhibited superior wear resistance compared with SS316. The most severe regime for SS316 was experienced at low angle of impingement, 45°, due to its ductility. Alternatively, the brittle network of chromium carbides showed significant impact on the behaviour of cast Stellite 6 under solid-liquid impingement with the most critical erosion-corrosion damage occurring at 60°

Effect of cathodic protection methods on ferrous engineering materials under corrosive wear conditions

Cathodic protection prolongs the service life of fluid transport and offshore engineering components by suppressing corrosion. This study assesses the effect of two cathodic protection methods, such as impressed current cathodic protection (ICCP) and sacrificial anode cathodic protection (SACP), on three ferrous-based materials under laboratory-controlled corrosive wear conditions. The SACP was as effective as ICCP on the protection of the low alloy steel and white chromium cast iron under both solid and solid-free corrosive wear conditions. Under solid–liquid impingement, significant reductions in the material loss were also observed in both the direct impingement zone and the outer area (oblique angle of attack). This demonstrates the substantial impact of cathodic protection systems that are exposed to erosion–corrosion dominated environments