Cr <sub> 2 </ Sub> O <sub> 3 </ Sub> Coating Dry Friction And Wear Properties

Cr₂O₃ coatings have found their wide applications serving as wear and corrosion resistant coating due to their high hardness,high chemical stability,low friction coefficient and excellent wear,corrosion resistance and heat resistance.These coatings have been successfully applied to sealing ring,piston,cylinder diesel engine and anilox so as to a great extent to extend the service lives for these important parts. However,friction and wear remains to be a predominant failure factor for these coatings in the applications.Therefore,it has great significance in investigating the prepare technology,friction and wear properties of Cr₂O₃ coatings.The microstructure,dry tribological behaviors and wear scar for Cr₂O₃ coatings sprayed by air plasma spray(APS)were investigated using pin-on-disk tribology, scanning electron microscopy(SEM),X-ray diffraction analysis(XRD)and energy dispersive spectroscopy(EDS).Besides,Four Cr₂O₃ coatings were prepared using four thermal spraying processes:flame spray,APS,improved APS and triple anode APS.The microstructure,hardness and adhesive strength for four coatings were comparatively investigated in this paper.Conclusion can be drawn as following:Orthogonal experiments were conducted to explore the influence of plasma spraying parameters on the tribological behaviours of Cr₂O₃ coatings.These parameters were composed by arc current,spray distance and flow rate of Argon and hydrogen.Experimental results showed that the optimized parameters were:plasma current 650A,Ar gas flow rate 40L/min,H₂ gas flow rate 10L/min,spray distance 100mm respectively.The dry wear behavior of air plasma sprayed Cr₂O₃ coatings against GCr15 steel was carried out at different loads and linear velocities at room temperature. Experimental results revealed that the weight loss for Cr₂O₃ coatings increased exponentially with the increase of loads and linear velocities.The friction coefficient for Cr₂O₃ coatings increased first and then decreased with rise of loads,but it decreased with increased sliding speed.It was found that the wear mechanisms of Cr₂O₃ coatings were governed by micro brittle fracture and adhesion wear observed by SEM and EDS.The properties of four coatings were also characterized.The results showed that flame sprayed Cr₂O₃ coating excelled in homogeneous microstructure,low porosity and few unmelt inclusion but low adhesive strength,however three APS coatings exhibited porous and inhomogeneous structure but higher adhesive strength than the former one.Dust removal treatment was beneficial for the reduction of unmelt inclusion,while triple anode plasma helped to improve the adhesive strength of APS coatings.