Cavitation erosion in silicon nitride: Experimental investigations on the mechanism of material degradation

First Results of Cavitation Erosion Behavior of Plasma Nitrided Niobium: Surface Modification

“…But, in the specialized literature, cavitation erosion behavior of plasma nitrided niobium has not been studied. Despite that significant research works have been done on the cavitation behavior of pure metals and metallic alloys, a much lesser degree of published works has studied the behavior of engineering ceramics [6][7][8][9][10][11][12][13] . Plasma nitriding technique was used here in order to obtain niobium nitride (ceramic-like material) surfaces formed in pure niobium substrates.…”

“…It was also observed by studying different ceramic materials that the possibility of exploring compressive stresses in surface layers would be an interesting prospect to improve the incubation period 6 . As presented in 8 , silicon nitride and zirconia has been reported as the technical ceramics with the best cavitation erosion resistance in the literature [6][7][8] , comprising the main subject for studies aiming to improve the performance of bearings, injectors or valves submitted to cavitation problem in real and different operating conditions, such as those verified in rocket engines 8,10,11 . Karunamurthy et al have also shown that cracking in cavitation eroded silicon nitride is preferentially intergranular, leading erosion pits to be produced.…”

“…Karunamurthy et al have also shown that cracking in cavitation eroded silicon nitride is preferentially intergranular, leading erosion pits to be produced. The presence of microcracks at the pits boundaries would result in a coalescence mechanism or pits bridging formation, leading more pits to be successively removed as the surface exposition to cavitation erosion goes on 10 . Finally, possible deformation and cracking mechanisms in the pit formation are presented in a study of cavitation exposure carried out in silicon nitride and zirconia 8 .…”

“…But, as it will be discussed hereafter, the main difference in this case is that the ceramic phase, supposedly formed at the substrate surface, comprises a nitrided layer obtained by nitrogen diffusion into a metallic bulk of the niobium substrate. So, the system 'surface + bulk' to be considered in this work would be formed by 'ceramic layer + metallic bulk', thus differing from those 'ceramic surface + ceramic bulk' as previously shown in references [6][7][8][9][10][11] .…”

Cavitation erosion damage of scroll steel plates by high-speed gas working fluid

“…Ultrasonic cavitation tests were conducted for different time periods starting from 1 h up to 8 h. The incubation pits, which were formed in the early stages of the cavitation mechanism, characterised as micro-pitting, can signifi cantly grow by linking, including cracks and grooves, general roughening of the surface [14,17,18]. The enlargement of the pits is accompanied by additional volume loss accelerating the erosion rate of the materials.…”