Ion implantation into inner wall surface of a 1-m-long steel tube by plasma source ion implantation

Nitrogen, oxygen and carbon ions were implanted into the inner wall of 316L austenitic type stainless steel tubes with inner diameters of 35 mm and 20 mm and 1-m length by a plasma source ion implantation (PSII). A 2.45-GHz microwave was fed into a tubular vacuum chamber and supplied to an antenna. Nitrogen, oxygen and acetylene gases were fed into the stainless steel tube. Plasma was produced by a coaxial electron cyclotron resonance (ECR) discharge. A magnetic field of 1 kgauss was generated by a solenoidal coil. The negative high voltage pulse of −20 kV was applied to the steel tube. During the implantation the solenoidal coil was moved along the axis direction of the chamber to allow uniform implantation for the axial direction of the tube. The result of Auger electron spectroscopy (AES) showed that uniform ion implantation into the inner wall surface of the 1-m length steel tube was achieved by PSII. Formation of a chromium nitride phase was confirmed for nitrogen ion implanted surfaces by X-ray photoelectron spectroscopy (XPS) measurement. Carbon implantation and subsequent diamond-like carbon (DLC) coating was confirmed for the inner wall surface treated by acetylene PSII from the measurements of Raman spectroscopy and scanning electron microscopy. The corrosion protection potential of the inner wall was improved by the ion implantation of all ion species, especially carbon ion implantation and subsequent DLC coating.