Mechanism of degradation of surface hardening at elevated temperature in TiAlV-alloys by in situ synchrotron radiation diffraction


Mechanism of degradation of surface hardening at elevated temperature in TiAlV-alloys by in situ synchrotron radiation diffraction

Berberich, F.; Matz, W.; Kreißig, U.; Schell, N.; Mücklich, A.

The surface hardness of the technically important alloy Ti–6Al–4V (wt.%) can be improved by nitrogen implantation. The structural mechanisms of hardening and of the stability of the improved hardness at elevated temperatures are studied. Ion implanted (II) and plasma immersion ion implanted (PII) samples were used. The formation of small TiN crystallites was detected in the as-implanted state, but only for the II samples a considerable surface hardness increase (factor 3) is observed. The in situ XRD experiments showed, that the TiN phase is stable up to temperatures of 650 °C for both types of implantation. At higher temperature Ti2N is formed which is stable up to 770 °C. ERDA results indicate a diffusion of nitrogen into the bulk material. The redistribution of N is responsible for the hardness changes: a slight decrease for II samples but an improvement by a factor of 2.5 for PII samples. The improvements/degradations of hardness and wear are discussed in correlation with the nitrogen depth distribution below the surface.

Keywords: Synchrotron radiation; Ion implantation; Hardening; Ti–6Al–4V

  • Nuclear Instruments & Methods B 199 (2003) 54-58

Permalink: https://www.hzdr.de/publications/Publ-5281
Publ.-Id: 5281