Abstract

The surface properties and cavitation erosion performance of NiTi/NiCr-75%Cr 3 C 2 composite coatings on AISI 304 stainless steel substance by atmospheric plasma spraying (APS) at different hydrogen gas flow rate were investigated. Composite coatings were characterized for microhardness. Microstructure of the cross section of composite coatings were investigated by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Caivation erosion test was finished by ultrasonic stretching vibration caviation test machine. The results show that when the hydrogen gas flow rate is 3L/min and 6L/min, the microhardness of coatings are respectively 640 HV and 730 HV at a load of 100 g and a dwell time of 15 s condition, and the composite coatings by APS generates porosity and were oxidized. The cavitation erosion resistance of composite coatings is better than that of nodular cast iron. As the hydrogen gas flow rate increases, the microstructure of composite coating deposited by APS has lower porosity, and the better cavitation erosion resistance.

Highlights

  • Cavitation erosion is caused by the internal pressure change of the liquid, which causes the dissolved gas in the liquid to nucleate, grow and collapse, and the cavitation collapse process will form a huge stress pulse, which will cause the surface damage of the material on the metal surface [1]

  • Cavitation is widely present in various types of hydraulic machinery, such as the propellers of ship, the cylinder liner, which will lead to premature component failure and even major accidents, resulting in heavy economic losses[2,3]

  • The NiTi alloys, which is famous for its excellent shape memory effect, has excellent super elasticity, wear resistance and cavitation erosion resistance

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Summary

Introduction

Cavitation erosion is caused by the internal pressure change of the liquid, which causes the dissolved gas in the liquid to nucleate, grow and collapse, and the cavitation collapse process will form a huge stress pulse, which will cause the surface damage of the material on the metal surface [1]. The NiTi alloys, which is famous for its excellent shape memory effect, has excellent super elasticity, wear resistance and cavitation erosion resistance. It is widely used in aviation, aerospace, machinery, transportation, chemistry, medical, energy and other fields[4,5]. An feasible method to prevent cavitation damages is to deposit the surface with NiTi coatings, such as explosive welding[7], cladding[8] and laser metal deposition[9] Among all these techniques, atmospheric plasma spray (APS) belongs to the most promising technique[10]. APS has widely used in industry in recent years due to its advantages of high flame and powder particles velocity, and an inert gas such as N2 is used for spraying, with which a dense coating with superior bond strength, low oxide content could be prepared

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