Performance of environment-friendly hydraulic fluids and material wear in cavitating conditions

The cavitation performance of various metals and hydraulic fluids used in a hydraulic system was evaluated using the vibratory test method. Mineral oil, vegetable oil and oil-in-water emulsions were used in the experiments. The materials were selected based on the general components employed in a hydraulic system—AA 5005 aluminium alloy, ASTM A536-84 ductile spheroidal graphite (SG) cast iron, ASTM A48-83 grey cast iron, AISI 303 stainless steel and BS 1400 LG2 bronze. It was observed that vegetable oil exhibits the best medium for erosion resistance for all metals due to its high viscosity index. Emulsions having higher oil concentration produced lesser erosion damage. It was seen that an increase in viscosity led to a decrease in the rate of growth and collapse of bubbles and hence reduced erosion on the surfaces of the specimens. The experiments also revealed that materials with high hardness had less cavitation damage for all lubricants. A comparison of cavitation performance revealed that materials and hydraulic fluids have a dependent relationship. Results indicate that AISI 303 stainless steel would be the best choice in the construction of a hydraulic system and this is especially the case when using a hydraulic fluid that has a high viscosity index.