Yoshimi Kagimoto

Improvement of Tribological Properties of Mosa Films by Forming Interlayers and/ or Bombarding with Ions

The effects of forming interlayers and/or bombarding with ions on the tribological properties of the sputter-deposited MoS 2 films were investigated. The MoS 2 films on substrates of Ti-alloy, martensitic stainless steel and high speed tool steel with TIN interlayers were evaluated by ball/disk sliding tests under ultra-high vacuum condition. Furthermore, nitrogen- or sulfer-ion-bombarded MoS 2 films tested too. The test results showed correlation between the surface hardness of substrates and the wear life of MoS 2 films. The wear life of the ion-bombarded MoS 2 films was improved by mixing film/substrate interface.

Adhered film formation on steel surface by impingement of hard particles

At the particle erosion test under high temperature condition, the instance that the adhesion of impinging particles made films on the worn surface of stainless steel was found. By the analysis of SEM and XMA, it was observed that the thickness of film was about from 5 to 15 μm and it was smaller than the average diameter of particles. Under 500°C condition stainless steel which covered with adhered film had almost equal wear resistance with cermet coating which was about five times as hard as stainless steel. Using the result of this test, the condition of the film formation was discussed. As a consequence, it was found that the state of the film formation under high temperature condition was concerned with the contact area between the particle and the test piece formed at the impingement.

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.

Boundary Lubrication Properties of Surface Modified Material Produced by Laser and Electron Beam Surface Alloying

The surface-modified material can be produced by laser and electron beam surface alloying of a plasma-sprayed molybdenum layer on Cr-Mo steel. The boundary lubrication properties and the metal structure of the surface alloy have been investigated. The main points of this study are as follows. 1. The surface alloy is thick, about 5 mm, and of uniform composition. 2. The surface alloy shows good wear resistance and good seizure resistance, in the same level as electroplated chromium and plasma-sprayed molybdenum layers. 3. Good wear resistance is attributable to the metal structure which is composed of hard M6C phase and soft α−Fe phase. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Diego, California, October 19–21, 1992