In addition, like Fig. 4(b) and (c), when the abnormal wear is generated by the initial partial contacting and the surface is once roughened severely, restoration by the subsequent operation becomes extremely difficult, and it is understood to be important to achieve excellent break-in condition in the initial wear condition in preventing the abnormal wear. It is clarified from the above-mentioned test results that the Ni-P + PTFE plating is effective in improving the initial break-in condition of the spray coated ceramics containing much ceramics.
3. Observation of Partial Contacting Sliding Surface
The sliding surface of the pin specimen after the partial contacting wear test was examined for the observation of the worn surface, EPMA analysis, and observation of the metallic luster area by jointly using various methods of observation in addition to the optical microscope and the surface roughness tester. In addition, two kinds of replicas of the sliding surface of the actual piston ring were sampled from the normal worn surface where the initial break-in condition was completed and from the worn surface where the abnormal wear was generated, the surface roughness was statistically processed, the quantitative interpretation on the break-in phenomenon was examined.
3.1 Test Method
3.1.1 Specimen and Test Conditions
For the surface observation, the pin specimen of the spray coated ceramics which was not plated after the partial contacting wear test was used. The specimen was used after the partial contacting operation of 20 Hr (number of revolutions： Max. 1400 rpm, load： Max. 5500N) was carried out, and then, the partial contacting wear test was carried out in 3 stages of the load x test time of 500N x 0.5 Hr, 1500N x 0.5 Hr, and 4500N x 0.5 Hr with the pin in the inclined condition.
3.1.2 Apparatus to be used
The three-dimensional SEM was used in addition to the regular optical microscope and the surface roughness tester to observe the sliding surface after the partial contacting wear test. In addition, the EPMA analysis was performed for the same view. For the observation of the metallic luster area (which is the molybdenum phase derived from the main composition of the spray coated ceramics as mentioned below) and for the measurement of the depth thereof, the mutual focus scanning laser microscope and the fringe scanning laser intervention microscope were used. To statistically process the data on the surface roughness, the statistical processing function among the analytical function of the three-dimensional SEM was used.
3.2 Test Results and Examination
3.2.1 Results of Observation of Worn Surface
Fig. 6 shows the results of observation of the sliding surface of the pin specimen after the partial contacting wear test. (a) shows the appearance of the sliding surface and the comparison of the surface profile, and the partially contacted part occupies the lower part of about 2/3 of the figure, and surface cracks that seemed to be attributable to high bearing pressure are generated over several parts. The sliding direction is the right-to-left direction in the figure, and enlargement of the area in the square frame at the center by the optical microscope is (b) in the figure. The part A where the crack is branched in three ways, and the crescent-shaped recessed part B in the vicinity thereof are shown in the figure. It is presumed from the results of observation by the optical microscope that the dark parts are cracks and recesses, but it is difficult to judge how deep they are in a quantitative manner, and they are projected or recessed.
In addition, the lustar area looking white looks projected at a glance. Though the depth of the crack was tried to be measured using the contact probe type roughness tester, but the depth of the part A could not be identified. The part in the vicinity of the related part was measured, but no parts that seemed to be a crack could be found from the results of measurement. The depth of the part B was also difficult to measure. Unless both the surface profile of the sample and the tip of the contact probe are simultaneously monitored by the microscope, etc., it is clearly difficult to measure the profile of the prescribed part by a general roughness tester.
The results of observation of the same part by the three-dimensional SEM is shown in Fig. 6(c). It is clearly understood that the rough profile of the sample surface becomes clearer. The part which was believed to be a crack (part A) was shallower than expected in the observation by the optical microscope, and the crescent-shaped recess (part B) which was unclear in the observation by the optical microscope can be recognized clearly. Though the regular SEM uses one detector, the present SEM is characterized in that four secondary electronic detectors parallel to X-axis and Y-axis orthogonal to each other in the sample surface and slightly inclined to Z-axis.
