Application of CVD method on grain-oriented electrical steel

Application of CVD method on grain-oriented electrical steel has been studied. Iron loss of grain-oriented electrical steel can be improved by thermal residual stress based on difference in thermal expansion between ceramic coating and steel substrate. Tensile stress on steel sheet enhances easy magnetization in the rolling direction. Required properties for the ceramic film are low thermal expansion, high elastic modulus and good adhesion, and nitride or carbide films are favorable from this point. For this purpose, TiN was deposited from a gas mixture of TiCl4, H2 and N2 using thermal CVD process at atmospheric pressure. TiCl4 was introduced into the reactor chamber by using H2 as a carrier gas. The deposition behavior of TiN was well explained by Langmuir–Hishelwood model taking the effect of HCl formation into account. High temperature deposition of TiN brought about strong tensile stress and achieved the extremely low iron loss. Deposition thickness of 1 μm was sufficient to keep superior adhesion and magnetic properties after stress relief annealing, 1073 K, 3 h in N2 atmosphere.