Effect of Nitrogen Addition on Synthesis of Nanocrystalline Diamond Films on Tungsten Carbide Substrate by Flame Combustion Method Using High-Purity Acetylene

Abstract

A flame combustion method enables the synthesis of diamond using acetylene-oxygen in ambient atmosphere. It has various advantages over other methods, such as in terms of speed, safety and cost. Tungsten carbide (WC) is used as cutting tools in the machining industry. In this study, to obtain nanocrystalline diamond films and to achieve good adhesion on the WC substrate, diamond films were synthesized by flame combustion using a mixture of high-purity acetylene and oxygen gas with the addition of nitrogen gas. Nitrogen gas added as the nanocrystalline diamond promotion agent; nitrogen flow rate was varied. The results indicated that, at the mixture of high-purity acetylene and oxygen gas, the diamond nanocrystallites was not synthesized on the diamond microcrystallites at nitrogen flow rate 0.000 cm3/s. As nitrogen flow rate was increased, the diamond nanocrystallites was synthesized on the microcrystallites. The diamond nanocrystallites was synthesized with high density all over the diamond microcrystallites.

Influence of Diamond Seed Attachment Processing on Diamond Films Synthesized on Tungsten Carbide Substrate by Flame Combustion

“…During the synthesis, the diamond film synthesis and delamination were affected when the distance was altered, because there was a change in the acetylene feather area. We confirmed that delamination at d = 7.0 mm during diamond film synthesis could be effectively prevented [14][15][16]. Therefore, diamond films were synthesized at d = 7.0 mm.…”

“…The synthesis conditions are listed in Table 1. These conditions have been determined and reported previously [14][15][16], and are believed to be the optimum conditions for preventing delamination during the synthesis of diamond films. The ratio of the oxygen flow rate (F o = 63.8 cm 3 /s) to acetylene flow rate (F a = 70.9 cm 3 /s) was set to R f = F o /F a = 0.90, because delamination-free crystallite growth could be realized at R f = 0.90 [14][15][16].…”

“…In this experiment, the film surface temperature was changed twice during synthesis [14][15][16]. The first step of the method was performed at 1273 K to achieve high bonding strength.…”

“…Therefore, diamond films were synthesized at d = 7.0 mm. The processing time for each of the two steps in the method used was set to 1200 s, and the total synthesis time for both steps was set to 2400 s [14][15][16]. The average thickness of the synthesized films was 30 μm/h.…”

“…We have also synthesized diamond films on a Ti substrate for dental implants using the flame combustion method [13]. In a previous report, diamond films were synthesized on WC substrates via flame combustion [14][15][16]. However, the synthesis of diamond films on WC substrates is difficult.…”