Technical Papers
Improvement of Initial Break-in Condition of Spray Coated Ceramics for Marine Diesel Engine
Tatsuhiro Jibiki**, Masaki Tanaka**, Takanori Fujiwara***, Masujirou Hisatani**
To avoid separation or abnormal wear of the spray coated ceramics caused by the partial contacting of the initial sliding, it is necessary to improve the initial surface break-in condition of the wear resistant spray coated ceramics of the piston ring and the cylinder linear of the marine diesel engine.
The partial contacting wear test of spray coated ceramics was carried out by using pin-on-disk type wear testing machine. The test results of spray coated ceramics with no treatment were compared with that of Ni-P + PTFE plated spray coated ceramics. An observation of wear surface was carried out using together some methods of observation in order to analyze the wear surface in initial break-in condition quantitatively.
The main results are in the following： Spray coated ceramics was worn abnormally after partial contacting wear test, but Ni-P + PTFE plated spray coated ceramics was worn normally, protecting from the damage by partial contacting. Phenomenon of surface break-in condition can be evaluated quantitatively by statistical processing of wear surface profile.
1. Introduction
The sliding condition between the piston ring and the cylinder liner of the marine diesel engine has been more and more strict recently, and attention has been paid recently to the spray coated ceramics containing much ceramics (hereinafter, referred to as "spray coated ceramics") as the sliding member capable of withstanding this condition. Though the spray coated ceramics is excellent in the wear resistance, it is inferior in the initial break-in condition, and when the strong partial high bearing pressure such as the partial contacting is generated in the beginning of the sliding, the coating separation or abnormal wear can be generated. To apply the spray coated ceramics to the actual engine, it is necessary to improve the initial break-in condition and to secure the durability and reliability.
The wear resistance is contradictory to the initial break-in condition in nature, and to improve the initial break-in condition of the spray coated ceramics, it is believed to be effective to newly add another coating.
In addition, to evaluate the effectiveness of the coating, it is believed to be important to experimentally reappear the partial contacting phenomenon due to the partial high bearing pressure by some method.
* Translated from Journal of MESJ Vol. 32, No. 12 (Manuscript Received July 29, 1997)
** Mitsui Engineering & Shipbuilding Co., Ltd. (Tamano City)
*** Okayama University (Okayama City)
In this report, the Ni-P + PTFE plated spray coated ceramics was examined as the coating to improve the initial break-in condition of the spray coated ceramics, and to confirm its effectiveness, the newly devised partial contacting wear test was carried out and the results were compared with those of the spray coated ceramics. Moreover, to observe the surface after break-in, various kinds of methods of observation including the optical microscope and the surface roughness tester were used together, and the method to quantitatively evaluate the break-in phenomenon was examined.
2. Partial Contacting Wear Test
2.1 Test Method
2.1.1 Specimen
In the partial contacting wear test, the piston ring side was taken as the pin specimen, and the cylinder liner side was taken as the disk specimen. Three projected test parts of the pin specimen are 5 mm in outside diameter, 2 mm in height, and 45 mm in sliding diameter, while the disk specimen is 57 mm in outside diameter and 8 mm in thickness. Both the pin specimen and the disk specimen are made of SUS403, and the spray coated ceramics of 50 vol.% Cr2O3 50 vol.% Mo cermet was formed by the plasma spray coating to the thickness of 250 μm on the test surface of both specimens, and the test surfaces were finished through surface grinding, and then, for the pin specimen, the Ni-P plating was formed on the spray coated ceramics to the thickness of 25 μm and the Ni-P + PTFE plated spray coated ceramics was formed on its surface to the thickness of 5 μm.
