DESIGN OF ION-IMPLANTED HYDROGEN CONTAMINATION BARRIER LAYERS FOR STEEL

The results of electrochemical hydrogen permeation tests are presented for a high strength low alloy steel of the type API 5L X-65 in the no n-implanted and nitrogen-ion-implanted conditions. The material was im planted under a variety of conditions to produce three series of sampl es, each with a characteristic implanted layer depth. The results for the implanted materials, when compared with the maximum hydrogen perme ability value determined for the nonimplanted material, indicate the e xistence of a critical implanted layer thickness. When the depth of an implanted layer is less than this critical value, the hydrogen permea bility of the composite material (implanted layer and substrate) is ob served to increase (relative to the non-implanted material). For layer thicknesses equal to or greater than the critical value, the permeabi lity is unnaffected or reduced respectively. It is concluded that nitr ogen-ion-implanted layers on steel are well suited for impeding hydrog en contamination and that the techniques employed in this study may be exploited to design surface-engineered hydrogen contamination barrier layers for steel.