Cavitation Erosion Performance Research Articles

Cavitation erosion behavior of laser gas nitrided Ti and Ti6Al4V alloy

A CW 2 kW neodymium-doped yttrium–aluminum–garnet (Nd-YAG) laser was used to carry out the gas nitriding process on commercial pure titanium and Ti6Al4V alloy. The microstructure, surface appearance, hardness depth profile and the cavitation erosion behavior of the nitrided samples in 3.5% NaCl solution were examined. The microstructure of the nitrided layer is mainly composed of TiN dendrites, of which the density gradually decreases towards the interface between the nitrided layer and the substrate. The cavitation erosion resistance of the nitrided samples was significantly improved as compared with the untreated samples. Increase in the surface hardness and the fine dendritic structure of the TiN layer contribute to the significantly enhanced cavitation erosion performance of Ti and Ti6Al4V alloy.

Microstructure/property relationships in the cavitation erosion of tungsten carbide–cobalt

The cavitation erosion performance of a range of tungsten carbide–cobalt (WC–Co) composites of varying grain sizes and cobalt contents has been evaluated using a stationary-specimen vibratory cavitation erosion rig. The WC grain size of the materials varied between 0.5 and 3 μm and the cobalt content between 6 and 15 wt.%. Two distinct regimes are observed in the cavitation erosion of the WC–Co grades tested: for materials with a WC grain size below 1 μm, the erosion resistance increases with decreasing cobalt content, while for materials with a WC grain size above this level, this trend is reversed. Microscopic examination of the eroded surface shows this transition to coincide with a change in material removal mechanism: sub-micron materials experience bulk material loss, while coarser materials display a localised response to erosive attack, which results in the preferential removal of the cobalt phase and the consequent loss of unsupported WC grains. It is proposed that this transition is related to a scaling effect similar to that observed in the particle erosion of composite materials. The relationship between the erosion response of the composite and its microstructural and mechanical properties in each regime is evaluated and discussed.

The solid particle and cavitation erosion of titanium aluminide intermetallic alloys

The mode of material removal during solid particle erosion and cavitation erosion of rolled super α 2 and plasma arc-melted γ titanium aluminide alloys have been investigated. These low density, high strength materials have potential application in turbine engine components, where the service conditions are potentially erosive, and there is a consequent interest in the erosion behaviour. Particle erosion tests were performed using an air blast rig, and vibratory equipment with a stationary specimen were used to investigate the cavitation erosion performance. Erosion rates were measured and characteristic damage features were identified on the surface of eroded specimens. The mechanisms of erosion are discussed in order to explain the promising performance of the materials in erosive conditions.

Cavitation Erosion Performance of Fiber Reinforced Composites

The cavitation damage resistance of several fiber reinforced polymeric composite systems was evaluated before and after seawater immersion via a modified ASTM G-32 method utilizing a stationary specimen. For both dry and saturated condi tions, a carbon fiber/thermoplastic toughened epoxy matrix composite (IM7/977-2T) was found to perform the best under cavitation attack, while carbon fiber/thermoplastic matrix (AS4/PEEK) was found to be the least resistant. Glass/epoxy composites (E-Glass/5920, Scotch Ply 1002) were intermediate in erosion resistance. Moisture absorption was seen to decrease the erosion resistance of both E-Glass/5920 and AS4/APC-2 materials, while increasing the resistance of SP 1002; IM7/977-2T was not affected by immersion. All mate rials show decreasing erosion rates due to material recession from the cavitation cloud and increasing collapse-shielding with exposure time. A reduction in water hammer pressure was estimated by incorporating finite material impedance into the water hammer equation. Using simplifying assumptions, a 15 percent reduction in water hammer pressure is calculated.

Comparison of cavitation erosion test results from venturi and vibratory facilities

A detailed comparison of cavitation erosion performance in tap water for five alloys in a vibratory (no-flow) system and a Venturi (flow) system was made. The effects of temperature variation (80 – 200 °F), Venturi throat velocity (34 – 49 m s −1) and vibratory horn double amplitude were studied. Correlations between maximum erosion rate (maximum mean depth of penetration rate (MDPR max)) and incubation period IP, and the material mechanical properties Brinell hardness and ultimate resilience UR = UTS 2 2E . (where UTS is the ultimate tensile strength and E is the elastic modulus), were examined. Only moderate success was achieved in correlations between “erosion resistance” MDPR max −1 and IP and these mechanical properties. However, a good correlation was found between MDPR max and IP, pertinent to both facilities, of the form MDPR max −1 = aIP n , where n is near unity (0.94). The cavitation intensity, as measured by MDPR max, was found to be 10–20 times greater in the vibratory system, depending on horn amplitude and material. This ratio varies between 5 and 30 if individual materials are considered separately, being greatest for 1018 carbon steel and least for 316 stainless steel. This indicates the important differences in form between these cavitating regimes and the imprecision of material comparisons made in both regimes.

Cavitation erosion performance and related properties of cured-sheet elastomeric coating systems : J. Z. Lichtman, J. Mater., 2 (3) (1967) 638–660; 16 figs., 7 tables, 9 refs.

Cavitation erosion performance and related properties of cured-sheet elastomeric coating systems : J. Z. Lichtman, J. Mater., 2 (3) (1967) 638–660; 16 figs., 7 tables, 9 refs.