EFFECT OF N2-TO-TICL4 FLOW-RATE RATIO ON THE PROPERTIES OF TIN COATINGS FORMED BY DC DISCHARGE PLASMA-ASSISTED CHEMICAL VAPOR-DEPOSITION

Attempts have been made to clarify the effect of the N2-to-TiCl4 flow rate ratio on properties of TiN coatings which were formed on M2 steel and pure iron at a temperature of 550 by a d.c. glow discharge method from mixed gases of TiCl4, N2, H2 and argon. The deposition rate of the coatings saturated at an N2-to-TiCl4 flow rate ratio of 8 to 9. The composition and hardness of the coatings remained unchanged with the N2-to-TiCl4 flow rate ratio except for the maximum ratio of 14.3, whereas the preferred orientation and microstructure changed markedly from (111) to (200), and from columnar to non-oriented. The coatings deposited at an N2-to-TiCl4 flow rate ratio of 3 to 6, which resulted in the (200) preferred orientation and fine grained dense structure, showed greater adhesion strength.