Development of New Generation Long Life Piston Ring Coating for 2 stroke Large Bore Marine Diesel Engines
Large-bore marine diesel engines equipped as main propulsion on ocean voyaging large vessels like container ships and crude oil tankers are supposed to possess very high reliability. One of the main factors that affects to the reliability of the main engines is the stable sliding of piston rings and cylinder liners. IHI Corporation and Diesel United have conducted jointly numerous basic experiments and tests on wear monitoring between piston rings and cylinder liners, and measurements of oil film thickness between piston rings and cylinder liners of main engines on vessels in commercial operation. The results obtained so far are utilized in clarifying the abnormal sliding mechanism between piston rings and cylinder liners that is hereafter referred as scuffing, and in developing effective cylinder lubrication methods that may be effective in preventing the scuffing. These activities have lasted almost ten years. The findings obtained clarified the following phenomenon. Namely, the scuffing is closely related to hard particles contained in the fuel oil (FCC), and to changes of engine operating conditions typically the engine speed. Poor lubrication of piston rings and cylinder liners to be caused by the above mentioned effect is clarified to induce the scuffing. Research results obtained during the period have clarified that the development of cylinder lubrication systems is quite effective in avoiding the poor cylinder lubrication. Furthermore, it is also important to develop the piston ring coating that may prevent the rapid growth of the scuffing phenomenon even when the poor cylinder lubrication being initiated, and that make the piston rings strong enough as to be immune to the presence of FCC on the sliding surfaces. Meanwhile, some ship owners prefer to have longer overhauling intervals matching with dry dock interval due to economic reasons. The scuffing resistance of piston rings and cylinder liners become extremely lowered when the piston ring coating is worn out in recently developed advanced engines which have higher output. Therefore, the life of the piston ring coating is required to be longer than the dry-dock intervals. Chromium ceramic coating is used as the piston ring coating that has relatively high reliability. However, further improvements with respect to the piston ring coating lifetime and scuffing resistance are required to be realized for satisfying the market demands. The present paper reports the new generation coating for piston rings which will be able to fills a demand of a market thus developed. The first step taken at the development is to clarify the sliding characteristics and the sliding mechanism between conventional plasma sprayed Mo coatings and chromium ceramic coatings. Plasma sprayed Mo coatings have high scuffing resistance with inferior coating life. Chromium ceramic coating films possess longer coating life than the plasma sprayed Mo coatings with lower scuffing resistance than the Mo coatings. Numerous basic studies and various measurement results obtained on operating ships in the present investigation have yielded a concept for new coatings that should have superior scuffing resistance as the Mo coatings possess, and longer coating life than that of chromium ceramic coatings possess as targets of the new coatings to be developed. The developed coatings are subjected to laboratory tests indicating the coatings to possess excellent properties. Namely, the developed coatings possess the scuffing resistance of about 1.8 times than that of conventional chromium ceramic coatings, and the coating life as longer as more than 4.3 times than that of the conventional chromium ceramic coatings. Furthermore, the developed coatings are confirmed to possess the same order of attacking property against the cylinder liners. Test conducted on operating ships have confirmed the same order of the coating life and superior sliding property as obtained at the laboratory tests. Thus, the actual applicability of the developed coating for main engines of operating vessels has been demonstrated.
Yoshiyuki Saito Takeshi Yamada Yoshiyuki Umemoto
IHI Corporation,Japan Diesel United,Ltd.,Japan
国际会议
上海
英文
1-12
2013-05-13（万方平台首次上网日期，不代表论文的发表时间）