Abstract
Friction and abrasive wear response of WC-12 Co and Cr3C2-25 NiCr coatings was studied. Abrasive wear experiments were conducted with SiC abrasive particles with varying load and sliding speeds. The results were analyzed using SEM, XRD and XPS observations of worn surfaces, wear debris and worn out abrasive paper. Friction coefficient diminished with rise in sliding speed and increased for increase in load while wear rates decreased for increasing sliding speed for both coatings. WC-12 Co coating had better wear resistance than Cr3C2-25 NiCr coating while Cr3C2-25 NiCr coating displayed lower friction coefficient. The variation in wear rate and friction response of coatings was due to combined effects of adhesion, abrasion and tribo oxidation effects. The composition of tribo films was strongly influenced by load and sliding velocity and altered friction and wear response of the coatings.
Highlights
Sprayed cermet coatings based on hard carbide phases like WC, and Cr3C2 are increasingly used for mitigation against high temperature, wear and corrosion to increase life of engineering components
Cr3C2-NiCr coating having nano crystalline grains (CNG) exhibited lower friction coefficient around than conventional grains coating (CGC) which was due to different material removal mechanisms 30
EDS spectra revealed the W, Co were the main elements in WC-12Co coating (Fig. 1c) while Cr, Ni were the main element in Cr3C2-25 NiCr coating (Fig. 1d)
Summary
Sprayed cermet coatings based on hard carbide phases like WC, and Cr3C2 are increasingly used for mitigation against high temperature, wear and corrosion to increase life of engineering components. High Velocity Oxy Fuel (HVOF) sprayed WC-Co and Cr3C2-NiCr coatings are suitable for different wear conditions due to higher hardness and good toughness. Carbide dissolution and formation of brittle carbides during thermal spraying process had significant influence on wear tribological behaviour of coatings . 1,10-14 HVOF process is the best method to deposit WC-Co and Cr3C2-NiCr type coatings as compared to other thermally sprayed techniques (e.g. plasma spray, detonation gun, flame spray etc.) . 15-19 High particle velocity and low flame temperature in HVOF process leads to low decomposition of WC and Cr3C2 particles, which has been reported beneficial for wear resistance of WC-Co and Cr3C2NiCr coatings . Cr3C2-NiCr coating having nano crystalline grains (CNG) exhibited lower friction coefficient around than conventional grains coating (CGC) which was due to different material removal mechanisms 30
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