Effects of B(CH3O)3 content on a PACVD plasma-boriding process

Investigations have been undertaken on the process of boriding by pulsed-DC plasma-assisted chemical vapor deposition technique (PACVD). The substrate material was 42CrMo4 steel. Boriding agent was trimethylborate [B(CH3O)3]. The flow rates of Ar and H2 were 2700 ml/min and 540 ml/min, respectively, the total pressure in chamber during plasma boriding process was 800 Pa, the boriding temperature was 830°C, the boriding time was 1 h and the flow rate of B(CH3O)3 was from 0.1 g/h to 1 g/h. A mass spectrometer was used to detect the ionization of B(CH3O)3. Experimental results showed that the boronized layer could be obtained under this testing process and the thickness of boronized layer increases with increasing the flow rate of B(CH3O)3. On the other hand, the B–C layer would be formed on the boronized layer when the flow rate of B(CH3O)3 was higher than 0.5 g/h and the thickness of B–C layer also increases with increasing the flow rate of B(CH3O)3.