Direct Coating of Nanocrystalline Diamond on Steel

Abstract

Nanocrystalline diamond films have been successfully deposited on stainless steel substrates without any substrate pretreatments to promote diamond nucleation, including the formation of interlayers. A low-temperature growth technique, 400 C or lower, in microwave plasma chemical vapor deposition using a surface-wave plasma has cleared up problems in diamond growth on ferrous materials, such as the surface graphitization, long incubation time, substrate softening, and poor adhesion. The deposited nanocrystalline diamond films on stainless steel exhibit good adhesion and tribological properties, such as a high wear resistance, a low friction coefficient, and a low aggression strength, at room temperature in air without lubrication. #

Low-temperature Growth of Nanocrystalline Diamond Films in Surface-wave Plasma

“…Figure 12.14 shows the obtained power spectra from the roughness profiles of the samples, i.e., the AISI 440C substrate without coatings and the NCD, ta-C and a-C:H films on the substrates. 23 The power spectrum obeys the power law in a specific region of wave number q for each sample, i.e., C(q) ¼ q Àa , as indicated by the solid lines. For the as-received AISI 440C stainless steel substrate with R a ¼ 3-4 nm in Figure 12.14 (a), C(q) obeys the power law in almost the entire region under study (0.01oqo10 mm À1 ).…”

“…In fact, this has been confirmed in surface-wave plasma CVD of NCD on stainless steel without any nucleation pretreatments. 23 In summarizing the foregoing discussion we have reached the following model for NCD growth in surface-wave plasmas. (1) Diamond crystals nucleate and grow into nuclei clusters of B3 nm in size in the plasma.…”

“…A relatively low sliding speed (10 mm s À1 , sliding amplitude: 10 mm, frequency: 0.5 Hz) was chosen in order to reflect the intrinsic friction property by avoiding external effects, such as lifting with speed. 23 Figure 12.12 shows the dynamic friction behavior of a film with a thickness of 1.7 mm up to 3600 cycles. 23 Two results from the different parts of the film are indicated in the figure.…”

“…23 Figure 12.12 shows the dynamic friction behavior of a film with a thickness of 1.7 mm up to 3600 cycles. 23 Two results from the different parts of the film are indicated in the figure. The friction coefficients for both the measurements tend to converge at values smaller than 0.1.…”

“…The average friction coefficient from further measurements is around 0.06, which is lower than that of generic diamond-like carbon (DLC). Figure 12.13 shows a summary of the results of the friction tests of a pinon-plate configuration using AISI 440C pin counterparts with a spherical sliding contact end of 30 mm radius with a normal load of 1 N. 23 We have also tested pristine stainless steel substrates without any coating and commercially available DLC films deposited on the same substrates for comparison. We selected two types of DLC films for the friction tests, i.e., hydrogen-free tetrahedral amorphous carbon (ta-C) and DLC with hydrogen inclusion (a-C:H).…”