Plasma immersion ion implantation of TiAl using chlorine containing plasma

In order to apply the protective effect of Cl doping for high-temperature oxidation resistance of TiAl alloys of complex-shaped parts, plasma immersion ion implantation (PI3) of chlorine into technical TiAl alloys was investigated. A specialized PI3 apparatus was optimized for the strongly etching electronegative Cl plasma. Plasma diagnostics was performed using a Langmuir probe. In order to sustain a sufficiently dense plasma, different RF antenna configurations are discussed and the resulting densities are compared. The influence of plasma pulsing on the surface interaction of Cl during the process was evaluated. Two different commercial alloys were implanted and tested. The resulting depth profiles of the modified surface layer were investigated using depth profiling with Auger electron spectroscopy (AES). After implantation, the Cl is located close to the surface. Oxidation tests at 900 °C in air for 100 h showed a strong decrease in oxidation, which is comparable to conventional beamline implantation of Cl. The effect is rather independent of the alloy composition.