Tribological properties of pure graphite under pv factors of 0.2-13.0 MPa·m/s in 70 ℃ 2 MPa water
A high temperature and high pressure water lubrication tribometer was used to simulate the water lubrication conditions of the canned motor nuclear main pump thrust bearing friction pair,the tribological properties of pure graphite against Stellite 12 alloy on a ring-on-ring configuration were investigated in 70 ℃(2 MPa)water with a fixed load of 900 N and a spindle speed of 100-6500 rpm under pv factors of 0.2-13.0 MPa·m/s.The results of Stribeck curves and continuous wear experiments demonstrate that the friction pair is in boundary lubrication under 0.2 MPa·m/s,exhibiting both abrasive and adhesive wear.The COF exceeds 0.05,with a maximal wear depth of 23 μm in graphite.A large number ploughs with widths exceeding 30 μ m and depths exceeding 4μ m are evident on the worn graphite surface due to WC scratches of Stellite 12 alloy.On the other hand,the width and depth of the plough on the Stellite 12 alloy worn surface due to WC loosening and flaking wear exceeded 2 μ m,accompanied by a large number of adherent wear graphite transfer layers and local cracking along the perpendicular to the direction of the plough.Under pv factor of 3.0 MPa·m/s,the friction pair was transformed into mixed lubrication.The COF stabilizes at 0.02-0.03,the wear depth of graphite decreases to 1.5 μm,and the number of ploughs on both graphite and Stellite 12 alloy surfaces decreases significantly.As the pv factor increases to 8.0 MPa·m/s,the friction pair transitions into a hydrodynamic lubrication regime.The COF stabilizes at 0.02-0.04,the wear depth decreases to 0.2 μ m,the surface of the graphite is"Disc print"with low surface roughness,and the surface of Stellite 12 alloy is polished,while the number of adherent graphite particles is reduced.
pure graphitepv factorhigh temperature and high pressure water lubricationstribeck curvewear mechanism
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