Freezing of sessile water droplets on titanium alloy surfaces with various roughness: An in-situ experimental study

The threat of icing caused by supercooled water droplets on aircraft components such as wings and compressors is a serious concern for aviation safety, and the surface roughness of these components can experience alterations due to environmental corrosion or damage. However, the potential impact of surface roughness variation on their susceptibility to icing remains unclear. In this study, the freezing experiments of sessile water droplets on the surfaces of a typical aero-engine titanium alloy (ZTC4) with varying roughness were conducted using a laser confocal micro-Raman spectrometer with a heating/freezing stage. Three freezing stages were captured via an optical microscope, and the temperature changes of water droplet during the cooling process were explored through heat transfer simulation. In addition, the relationship between Raman peaks and temperatures of frozen droplets was quantified. The results of 200 repeated experiments demonstrated that the freezing temperatures of sessile water droplets exhibited a two-parameter Weibull distribution, and there was a nonlinear positive correlation between the mean freezing temperature and surface roughness, which implied that environmental corrosion or damage leading to an increase in surface roughness may significantly elevate the probability of component icing and safety issues.