Erosion characteristics of surface hardened Ni–Al bronze

Abstract

Surface hardness characteristics and erosion resistance of Ni–Al bronze produced by three kinds of quenching have been determined to assess their potential as surface treatments for marine propellers. Flame, high frequency, and laser processing were employed as the surface hardening treatments. Microstructures and distributions of alloying elements were examined using microscopy, computer image analysis, and EP MA. Jominy and ultrasonic erosion tests were also conducted to evaluate the depth of surface hardening andresistance to propeller cavitation erosion. The experiments revealed that Ni–Al bronze has quenching characteristics closely related to those of steel and that bronze surface hardened by flame quenching is about 1·5 times harder than as cast. It was also found that lame quenching is the most suitable technique for surface treatment of propellers.

Cavitation erosion of Cr60Ni40 coatings generated by friction surfacing

“…For the Cr-rich constituent the better wear behavior of the coatings can be attributed to the much finer needleshaped precipitates compared to the cast and heat treated state. It has been found in other studies that grain refinement alone can lead to an improved wear resistance against cavitation erosion [12,18]. However, the internal structure of these constituents is not fully understood yet, and proof of the different phases present as well as their mechanical properties still needs to be investigated.…”

“…This is a mechanism found regularly on surfaces exposed to cavitation, and is due to the mechanical impact stresses caused by imploding cavitation bubbles. If two adjacent grains or phases have different strength and ductility, the strain will be larger in the weaker phase, leading to stresses within the boundary [12,18]. Within the eutectic the fcc NiCr solid solution obviously is the weaker phase and protrudes in between the harder CrNi lamellae.…”