Results from experiments on hybrid plasma immersion ion implantation/nitriding processing of materials

To improve the performance of critical part components, new methods for surface strengthening are being developed with success, like plasma immersion ion implantation (PIII) and hybrid surface treatments mixing PIII and ion nitriding processes. A combination of high pressure (4 × 10¹Pa), moderate temperature (up to 450ºC) glow discharge nitriding with low pressure (8 × 10-2Pa) and low DC bias voltage ion nitriding (or DC PIII) was implemented. Depending on the particular conditions of the treatment and the depth probed, mixed phases of gammaN and epsilon were measured in the treated SS304 steel sample. This near surface modification resulted in an improved hardness (up to a factor of 2.7 ×) of the sample which could also enhance its wear properties. Surface modification of Ti6Al4V alloy and SS304 steel by a combination of PIII and subsequent ion nitriding was investigated as well. Nitrogen ions were implanted into the specimens at 15 keV and then ion nitrided at low pressure (7 × 10-2Pa) with a bias of -800 V. Compared to the untreated samples, the hardness of Ti6Al4V alloy and the steels could be improved significantly. AES results indicated high retained doses in both samples, confirming the high efficiency of this hybrid process.