This structure is simply referred to as Ni-P + PTFE plating. The bonding coat between the spray coated ceramics and the base material was formed to the thickness of 100 μm with Mo as the main composition. The surface hardness of the formed spray coated ceramics was about Hv800, while the surface hardness of the Ni-P + PTFE plating was about Hv500.

　

Fig. 1　Schematic illustration of pin on disk wear testing machine

　

2.1.2　Method of Partial Contacting Wear Test

The pin-on-disk type wear testing machine shown in Fig. 1 was used as a testing machine. The pin specimen of the shape where three disk-shaped projections were projected and the disk-shaped disk specimen were brought into contact with each other in a stacking manner in the vertical direction, and the test specimens were rotated under the load.

The partial contacting wear test was carried out as follows. That means, a notch as indicated in Fig. 2 was provided in each end part of the pin specimen so as to be flexible, a metallic sheet (a SUS sheet of 100 μm in thickness) was held in an outer circumferential part of the pin specimen, and fixed to the pin holder with the pin specimen in the inclined condition. The inclination of the pin specimen was about 30 μm5000 μm, which means, the difference in height of 30μm was generated at each end part of the pin of 5 mm in outside diameter. The ratio of inclination was approximately doubled so that the partial contacting effect is more remarkable, referring to the results measured by the actual piston ring.

　

2.1.3　Test Conditions

The test was carried out by immersing both test specimens in the lubricating oil. Though the temperature of the lubricating oil was not specially controlled, it rises up to about 393K by the friction heat. The test condition of the number of revolutions was set to be constant of 900 rpm (the sliding speed： 2.1 m/s). As for the load which seems especially important in the partial contacting test, the combination of the load x test time with the same test specimen was classified into three stages of 1500N x 0.5 Hr. 4500N x 0.5 Hr, and 4500N x 20 Hr. Prior to the partial contacting wear test, the contacting operation (under the condition of the number of revolutions of Max. 1400 rpm, and the load of Max. 5500 N) was performed only for the pin specimen with spray coated ceramics. The lubricating oil used in the test was SAE#20 Diesel Engine Oil (viscosity;58.78 cSt, @313K,8.207 cSt. @373K, denisity：0.8894 g/cm³).

　

Fig. 2 Method of partial contacting wear test

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