Volume 4, Issue 9 (October 2007)
Coriolis Erosion Testing Approach for Relatively Thick Coatings
To meet the challenge of wear and corrosion attack in various applications, coating has been an effective protection approach for the work surface of engineering components, including slurry pump wet-end parts (e.g., impellers, liners, and shells). The coated wear parts that handle flowing slurry are exposed to both sliding and impact erosion along with possible corrosion factors. In such erosive wear conditions, relatively thick coatings including overlays may be needed to extend service life of the wear components. Different wear testing methods have been used to evaluate the tribological properties of coating materials under both dry and wet wear conditions. Previous studies have shown that Coriolis erosion testing is a valuable and effective approach to study erosive wear behaviors of materials in flowing slurry conditions such as within a centrifugal slurry pump system. Although extensive research can be found on wear of hard coating materials, coating erosive wear research conducted using Coriolis wear testing methods is very limited. This paper demonstrates that Coriolis erosion testing can be applicable for both sliding and impact wear on relatively thick coatings (typically, 250 μm or thicker). By adjusting test parameters within the Coriolis erosion testing system, such as flow rate (or solids particle velocity), solids type, size, and concentration, and impact angle, various types of coatings can be tested for different erosive wear conditions. Through such Coriolis erosion testing, erosion rate and tribological characteristics of coatings can be determined and evaluated. The coating examples used in this study include NiCrSiB, NiWCrSiB, WC-NiCrSiB, and WC-Co-Cr coatings produced with flame-spray, sintering and/or high-velocity-oxygen-fuel (HVOF) and high-velocity-air-fuel (HVAF) processes. Some related factors have also been discussed.