A determination was made of the conditions favorable to the deposition and diffusion of Si
3N
4 on SKD11 steel substrates by means of an inductively coupled, externally heated plasma discharge and a push-pull Hartley RF (13.56-MHz) oscillator using a triode and having a maximum output of 70W was disigned. The reactive gases NH
3 and SiN
4 were diluted with Ar to a prescribed concentration. Test pieces of SKD11 measuring 5×5×0.5mm were prepared, thier surfaced were polished using diamond paste, and the Si
3N
4 was deposited onto the surface.
By means of experiments based on a method using orthogonal table L27, it was found that the optimum distance between the test pieces and the oscillator electrode was 25cm, and the optimum ratio between NH
3 and SiH
4 was 1:2.5 at 1073K. The relationship between the distance between the test pieces and the oscillator electrode and the reaction temperature was 5% significant for the thickness of the diffusion layer.
Investigation of the apparent activation enerty of the growth of the diffusion layer of Si
3N
4 yielded a value of 78.7kJ/mol at 1023K-1073K.
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