Friction Behavior of High Velocity Oxygen Fuel (HVOF) Thermal Spray Coating Layer of Nano WC-Co Powder
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초록
High Velocity Oxygen Fuel (HVOF) thermal spray coating of nano size WC-Co powder (nWC-Co) hasbeen studied as one of the most promising candidate for the possible replacement of the traditional hardplating in some area which causes environmental and health problems. nWC-Co powder was coated on Inconel718 substrates by HVOF technique. The optimal coating process obtained from the best surface propertiessuch as hardness and porosity is the process of oxygen flow rate (FR) 38 FMR, hydrogen FR 57 FMRand feed rate 35 g/min at spray distance 6 inch for both surface temperature 25oC and 500oC. In coatingprocess a small portion of hard WC decomposes to less hard W2C, W and C at the temperature higherthan its decomposition temperature 1,250oC resulting in hardness decrease and porosity increase. Frictioncoefficient increases with increasing coating surface temperature from 0.55-0.64 at 25oC to 0.65-0.76 at 500oCdue to the increase of adhesion between coating and counter sliding surface. Hardness of nWC-Co is higheror comparable to those of other hard coatings, such as Al2O3, Cr, Cr2O3 and HVOF Tribaloy 400 (T400). This shows that nWC-Co is recommendable for durability improvement coating on machine components suchas high speed spindle.
Abstract
High Velocity Oxygen Fuel (HVOF) thermal spray coating of nano size WC-Co powder (nWC-Co) hasbeen studied as one of the most promising candidate for the possible replacement of the traditional hardplating in some area which causes environmental and health problems. nWC-Co powder was coated on Inconel718 substrates by HVOF technique. The optimal coating process obtained from the best surface propertiessuch as hardness and porosity is the process of oxygen flow rate (FR) 38 FMR, hydrogen FR 57 FMRand feed rate 35 g/min at spray distance 6 inch for both surface temperature 25oC and 500oC. In coatingprocess a small portion of hard WC decomposes to less hard W2C, W and C at the temperature higherthan its decomposition temperature 1,250oC resulting in hardness decrease and porosity increase. Frictioncoefficient increases with increasing coating surface temperature from 0.55-0.64 at 25oC to 0.65-0.76 at 500oCdue to the increase of adhesion between coating and counter sliding surface. Hardness of nWC-Co is higheror comparable to those of other hard coatings, such as Al2O3, Cr, Cr2O3 and HVOF Tribaloy 400 (T400). This shows that nWC-Co is recommendable for durability improvement coating on machine components suchas high speed spindle.
참고문헌 (3)
- "HVOF ThermalSpray Coatings as an Alternative to Hard ChromePlating on Military & Comercial Aircraft AESF", EPA Conference for Environmental Excellence, 1~20
- "Handbook of Thermal Spray Technology", pp.1~30
- "HVOF Coatingof Co-alloy T80 for the Improvement of thePerformance and Durability of Military HardwareComponents", pp.~15