Recently, the lifetime extension of nuclear power plant is rearing so it is necessary to have facility safety management and economical management.
However, when bolts in nuclear power plant are replaced and turbine overhauls for nuclear power plant are disassembled, there are lot of problems due to an occurrence of stuck bolt in clamping part. In order to solve these problems, first, hybrid vacuum chamber was designed and manufactured which can deposit Arc ion plating and Sputtering. So with the method of Arc ion plating and Sputtering, we used the machine to deposit TiN on A913 B7 bolt.
The compositions and characteristics of the bolt which are XRD and SEM and the mechanical properties of tensile strength, yield strength and elongation were analyzed and through corrosion rate test, neutral salt spray test, block test and irradiation exposure test, it was tested how long the bolt can endure various conditions in nuclear power plant. In the result of observation of SEM and XRD, the continual and even coating layer was clearly seen. In the test of corrosion characteristics of a boric acid solution, TiN coating bolt showed the least corrosion rate and had the least external transition.
Characteristics of the base material were not changed due to the coating deposition. The coating deposition does not interfere with the base material characteristics. Through the neutral salt spray test, the TiN bolt was able to endure in brine for 200 hours.
Through Irradiation exposure test, the specimen's test result was confirmed that the mechanical properties are preserved comparing to radiation gamma irradiation before. When this TiN coating bolt are used to a nuclear power plant, lifetime can be extended compared to conventional bolt, but it needs to be checked what kind of properties are required additionally.