Influence of thin-film wear-resistant cermet coatings of crankshaft journals on the performance characteristics of marine diesel engine friction-type bearings

Medium-speed diesel engines installed on marine vessels serve as main and auxiliary engines having crankshaft necks with hardness ranging from 164 to 694 HV (58 HRC) and different types of bearing liners. The main reasons for the failures of crankshafts are wear and scuffing of the necks. Scuffing of the necks and melting of bearing antifriction layer often lead to deformation of crankshafts, and occasionally to their breakdown. Wear resistance of friction surfaces of the tribo-component parts is the main factor determining the service life and operating costs, as well as the need for repair. The solution to the problem of increasing wear resistance and, correspondingly, durability is associated with the application of various methods of hardening friction surfaces and tribo-active additives to lubrication. Currently, a large group of tribotechnical materials is used to harden friction surfaces by modifying and forming a cermet layer on the mating surfaces due to the energy generated in the process of friction, which by many criteria exceeds the wear-resistant coatings obtained when applying traditional technological methods of hardening. However, there are often no recommendations on the effective use of a particular preparation for such an important tribo-component as the crankshaft bearings of the medium-speed diesel engine. Therefore, in shipboard practice, tribo-preparations are rarely used to increase the life time and operating efficiency of the crankshaft bearings of medium-speed diesel. The article presents the tribotechnical characteristics of friction-type bearings with a vermiculite-based cermet coating of shaft necks, and an assessment of the effectiveness of its use for treating crankshafts of ship diesel engines with different hardness of shaft necks