Investigation of cryogenic quenching of metal surfaces with various coatings

Cryogenic quenching is frequently encountered in many applications like LNG technology, cryogenic preservation of biomaterials, cryogenic material machining etc., in which one key issue is to accelerate the temperature decrease so as to achieve large cooling rate. In the present study, the cryogenic quenching experiments are conducted by immersing the metal rodlets with various coating layers at room temperature into a liquid nitrogen bath. It is found that fast cryogenic quenching of the aluminium alloy rodlet with a higher Leidenfrost temperature is achieved by coating a thin layer of nano-structure with nanopores on the outer surface. In addition, the similar method of surface fabrication is applied to the stainless steel rodlet and a moderate reduction of quenching time in liquid nitrogen is achieved. Furthermore, the cryogenic quenching of stainless steel rodlets coated with the Teflon layers is also investigated.