Valve Core Strength Combined With High Density Coating Process And Device Research

Liquefied natural gas(LNG) as a new energy has been widely applied in residents’ daily life, and the quantity demand grows very rapidly in the following years. Due to liquefied natural gas is easy to spread and leak, the high security devices are essential for production, receive, transportation and gasification and so on. The cryogenic valves play a very vital role for the safe and reliable operation of these systems. Since cryogenic valves work in the harsh working conditions, it is necessary to study low temperature material performance and related equipment.In this paper, Ni60 fluxed nickel-based powder and Ni60+15%316 composite powder was sprayed on the surface of the valve core sample by high velocity oxygen fuel. Then some of samples were selected to remelt in the furnace for post-treatment. After that, all the samples with coating were set in the low temperature condition for impact test. After the low temperature impact test, a series of test were done such as hardness test, the bond strength between substrate and coating, microstructure analysis of coating, porosity value test, XRD phase analysis, wear testing etc. Through the analyze the data of above tests, the conclusions are shown in the follows: the furnace re-melting processing after spraying process can lead the porosity value of coating decrease significantly, the bonding strength improve, hardness and wear resistance of coating is greatly improved. Meanwhile the way of combination between coating and base material change from "mechanical bond style" to "metallurgical bond style". Under the comprehensive consideration, the Ni60 powder which sprayed using high velocity oxygen fuel with furnace remelting post-treatment process show the best comprehensive properties.Based on supersonic flame spraying processing and furnace remelting post-processing technology, the wear resistance and low temperature resistance of cryogenic valves material can improve effectively. At the same time, it can reduce the maintenance frequency and extend the service lifetime of the valve. At last, it can make good economic benefit in society.