Cavitation Resistance of WC-10Co4Cr and WC-20CrC-7Ni HVAF Coatings

Abstract

Machines operating in aqueous environments may be subjected to cavitation damage during operation. This study aims to evaluate the cavitation resistance of WC-10Co4Cr and WC-20CrC-7Ni coatings under cavitation erosion conditions with additional electrochemical effects. The coatings were deposited on AISI 1040 steel substrates using a high velocity air fuel thermal spray process. The microstructure of the coatings was observed by a scanning electron microscope, while their phase composition was analyzed using an energy-dispersive microanalysis system. In addition, the microhardness of the coatings and substrate was measured, and the surface topography of the eroded surface layers was observed using a 3D optical profilometer. The results revealed that the cavitation resistance of the WC-20CrC-7Ni coatings was better than that of the WC-10Co4Cr coatings. The observation of the structure and surface topography made it possible to identity the reasons for the differences between the cavitation resistance of both coatings: The WC-20CrC-7Ni coatings had a finer grain structure, lower pore density, and lower as-sprayed surface roughness. These differences, along with the presence of a high Cr and Ni content in the feedstock powder, that increased the coating corrosion resistance, contributed to improving the cavitation resistance and reducing the material loss of the WC-20CrC-7Ni coatings.Keywords cavitation erosion resistance Á HVAF coatings Á microstructure Á surface topography Á ultrasonic vibration method Á WC-10Co4Cr Á WC-20CrC-7NiThis article is an invited paper selected from presentations at the 2021 International Thermal Spray Conference, ITSC2021, that was held virtually May 25-28, 2021 due to travel restrictions related to the coronavirus (COVID-19) pandemic. It has been expanded from the original presentation.

Corrosion behavior and mechanism of X80 steel in silty soil under the combined effect of salt and temperature

“…It could provide qualitative images at the microscale level and further evaluate the degree of corrosion surface coverage. 32 The results of measurements are shown in Fig. 8 and 9 .…”

Advanced ceramics and coatings for erosion‐related applications in mineral and oil and gas production: A technical review

“…Different surface engineering technologies, particularly coating processing options, such as electroplating and electroless technologies, thermal spray, microwave cladding, friction stir processing, plasma‐assisting technology, PVD, CVD, and some others can be basically considered and employed for steel protection by hard layers. Ceramic (oxide and non‐oxide) or composite protective layers (e.g., CMC, MMC, and DLC) have higher potential 124–136 . However, many of the listed options are not well suited for industrial applications in mining and mineral processing, either because they cannot withstand severe abrasive and erosive conditions required by the industry, or because they are not applicable for the inner surface protection of long tubing and complex shape components.…”

High-velocity air fuel coatings for steel for erosion-resistant applications

“…Varis et al [10] proposed that high compressive stresses of HVAF-coatings inhibit the fatigue crack formation and propagation along the microstructure consisting of lamellae interfaces, thus improving the cavitation resistance of the coating. According to Korobov et al [9], the fine structure of WC-CrC-Ni coating increases the specific surface area of carbide particles and, consequently, the required crack propagation energy.…”

“…In turn, this improves their resistance to chipping and consequently, to cavitation compared to the coarser WC-CoCr coating (Figure 7). In the case of the WC-CrC-Ni coating, the hardening of the matrix caused by the dissolution of Cr is accompanied by an increase in the matrix's plasticity, which prevents carbides from detaching from the matrix [9]. Kumar et al [18] reported that spraying parameters (e.g., particle velocity) affected the mechanical properties of HVAF-sprayed tungsten carbide coatings (e.g., fracture toughness), influencing the resultant cavitation resistance.…”

“…Consequently, dense, highly cohesive coatings with low porosity, and superior wear performance can be deposited via HVAF [4,6,8]. Therefore, HVAF-coatings tend to exhibit higher mechanical properties (i.e., fracture toughness, elasticity modulus, hardness, and compressive strength) than HVOF-coatings [5,9] due to the abovementioned advantages.…”