Toshikazu Hayashi

Seizure Tests to Select Materials for Cylinder Blocks and Valve Plates in Water Hydraulic Pumps

For application to water hydraulic pumps (axial piston type), influence of material combination and micro shapes of sliding surfaces on friction and seizure were experimentally investigated. Seizure tests under water lubricating condition were carried out by an end-face sliding test apparatus, and sliding pairs containing diamond-like carbon (DLC) coating which is considered one of hopeful materials by its excellent tribological property in water were prepared for the seizure tests. As a result of the seizure tests it is obtained that in combination of stainless steel and DLC coating critical contact pressure on occurrence of seizure increases with increase of radius of pads edge of a stationary specimen. On the other hand, a result of the tests shows that combination of aluminium bronze and DLC coating has much higher critical contact pressure on occurrence of seizure than combination of stainless steel and DLC when micro shapes of sliding surfaces are similar. For application of DLC coatings to valve plates in water hydraulic pumps it is better to choose copper alloys as mating surfaces of DLC coating and it is required to round edges of pads on valve plates adequately.