Effects of the duty factor on the surface characteristics of the plasma nitrided and diamond-like carbon coated high-speed steels

The purpose of this study is to investigate the effects of the duty factor on the surface characteristics of plasma nitrided and diamond-like carbon ( DLC) coated high-speed steels. In the duplex treatment. pulsed plasma nitri ding was performed with N-2 and H-2 gases at 530 degrees C for 4 h. Duty fa ctors were controlled within the range from 0.1 to 1 by varying both the pu lse-on time and the pulse-off time. Plasma-assisted chemical vapor depositi on equipment was used for the deposition of DLC films. Since the adhesion o f the him to the substrate is of primary importance for the industrial appl ication of duplex layers, the critical load was measured by the scratch tes t method. Properties of the nitrided and duplex treated layer were analyzed by using optical microscopy, scanning electron microscopy, X-ray diffracto metry, atomic force microscopy and micro-Vickers hardness measurement. It w as found that surface roughness increased with increasing duty factor for a ll the nitrided and duplex treated surfaces. The critical load to failure d ecreased with increasing substrate roughness. (C) 2000 Elsevier Science S.A . All rights reserved.