Materials and technologies for rebuilding ship propellers blades damaged under cavitation attack: history and current state

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Materials used for manufacturing ship propellers were listed, and classification of technologies of repairing ship propellers with cavitation wear spots was cited. The characteristics of materials used in the technologies were given. The advantages and disadvantages of the repair through deposition by welding as main technology at present time were listed. Alloys most resistant to cavitation wear were considered: dispersion-hardening alloys and alloys, in which the phase transformation occurs in cavitation impacts. The low manufacturability of mentioned alloys was pointed to, that is the principal cause of the fact that these alloys did not have a wide distribution in ship propellers repair. In modern practice of deposition by welding, the filler materials close by composition to the propeller alloys are used, and priority is given to regular recovery of surface quality and not to the rise in the surface wear-resistance. Improvement of the welding technology is now directed at the development of technological methods to raise the wear resistance, that is the methods, not based on the using the filler materials different from ship propellers materials. The advantage of the use of polymeric materials to repair the cavitation wear spots on the blades is noted. All the repair compounds are made of thermosetеtting resins, the most widespread of which are epoxy compounds. The peculiarities of cavitation attack on the blade surface in service are analyzed. It was mentioned that polymeric compounds being used nowadays are developed without taking into account these peculiarities. One has to draw attention to that the longevity of polymeric compound under propeller cavitation is determined in many respects by the adhesion of polymer to propeller material. A solution for the problem of the low adhesion of the polymer compounds to the propellers alloys will displace the repair technology based on the deposition by welding in future.