Cavitation erosion and jet impingement erosion can result in a great loss of materials. NiTi alloy is a very promising candidate to acquire cavitation erosion resistance and jet impingement erosion resistance because of its superelasticity. Due to the high cost and poor workability of NiTi alloy, many people tried to overcome such drawbacks by preparing NiTi coatings on the basis of deteriorating the good properties as little as possible. From the aspect of the application of NiTi coating, the erosion resistance should be evaluated comprehensively. One of these evaluations involves the comparison of cavitation erosion resistance and jet impingement erosion resistance of NiTi. This evaluation has not been made thus far. Thus, in this study, the NiTi coating was prepared by air plasma spraying (APS) using pre-alloyed NiTi powder. Its microstructure, chemical composition and phase transformation were identified. Cavitation erosion behavior and jet impingement erosion behavior of the as-sprayed NiTi coating were compared. The results showed that the coating exhibited better jet impingement erosion resistance than cavitation erosion resistance. This was attributed to the oxides, impurities, cracks and pores that existed in the coating, whose effects on deteriorating the cavitation erosion were far greater than those worsening the jet impingement erosion.
The NiTi cladding with/without Ni interlayer was prepared on stainless steel (SS) by tungsten inert gas (TIG) surfacing process, aiming at achieving good cavitation erosion resistance. The ranking according to the cavitation erosion resistance is NiTi plate > NiTi-Ni-TIG cladding > NiTi-TIG cladding > SS. The better cavitation erosion resistance of NiTi-TIG and NiTi-Ni-TIG claddings than SS substrate is due to their higher micro-hardness and superelasticity. Furthermore, the existence of Ni interlayer can decrease the amount of brittle intermetallic compounds, such as Fe 2 Ti, and inhibit the crack generation, which results in the higher cavitation erosion resistance of NiTi-Ni-TIG compared with NiTi-TIG cladding. Thus, the cavitation erosion resistance of NiTi cladding prepared by TIG surfacing process can be improved by employing Ni interlayer.
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