Nitriding of H-12 tool steel by direct-current and pulsed plasmas

Direct-current (DC) and pulsed plasmas were used to nitride samples of AISI H-12 tool steel with treatment time varying from 1 h to 6 h. X-ray diffrac tion (glancing-angle and theta-2 theta geometry), conversion electron Mossb auer spectroscopy, conversion S-ray Mossbauer spectroscopy and Vickers micr ohardness were used as analytical techniques. The near-surface compound lay er consists of a mixture of gamma'-Fe4N and epsilon-Fe-x(N,C), while the ne ar-diffusion zone compound layer consists of a mixture of y'-Fe4N, epsilon- Fe-x(N,C), alpha''-Fe16N2 and gamma-austenite. For a DC plasma the dependen ce of compound layer thickness on nitriding time obeys a parabolic law, but for a pulsed plasma this dependence does not follow a parabolic law. (C) 1 999 Elsevier Science S.A. All rights reserved.