Plasma immersion ion implantation of cylindrical bore using self-excited radio-frequency glow discharge

Plasma immersion ion implantation (PIII) is an effective surface processing technique. However, it is still difficult to implant the inner wall of a cylindrical bore using this technique due to the internal small-volume effect. This paper presents a new approach based on self-excited radio-frequency (RF) glow discharge inside the tube. The tube which itself acts as a plasma source to generate the required plasma is biased negatively to conduct PIII. Steady discharge and plasma generation can be achieved and the plasma density is generally quite uniform in spite of the end effect of glow discharge. To demonstrate the technique, a stainless steel tube 30 mm in diameter and 200 mm long is implanted. The XPS results show that nitrogen PIII is indeed successful and phases such as Cr 2O 3, CrN, and FeN are formed from the nitrogen implanted layer which improves the wear resistance of the stainless steel tube. Our results reveal uniform improvement along the tube axis suggesting that this novel technique is an effective tool to implant the inner wall of a cylindrical bore.