SUS 304 stainless steel and Fe were implanted with 1×1017 Ti+/cm2 at room temperature. The surface composition of implanted SUS 304 and Fe at high temperatures was observed in vacuum with AES and XPS.
The precipitation of Ti compounds was found on the surfaces of implanted SUS 304 and Fe. Implanted Ti+ into SUS 304 and Fe, which existed near the surfaces of metals, diffused into the inside of the surfaces and reacted on C and N in metals. At about 600 K, TiC precipitated on the surfaces of both SUS 304 and Fe. The precipitated TiC disappeared at about 1100 K and TiN precipitated on the surface of SUS 304, while on the surface of Fe this change was observed at about 750 K.
The surface precipitation behavior is explained as follows: As TiN is thermodynamically more stable than TiC, the latter reacts on N which diffuses from the bulk of metal, and changes into TiN. The diffusion coefficient of N in Fe is larger than that of N in SUS 304. Therefore, the precipitation temperature of TiN on the surface of Fe is lower than on that of SUS 304.
This precipitation behavior can be applied to the surface treatment of various metals.
