抄録
Using CVD, tungsten coatings were deposited on iron substrates, and SiC coatings on tungsten substrates, and based on the results obtained, SiC coatings were deposited on the tungsten-coated iron.
(1) Tungsten coatings on iron. Using the reaction WCl6(g)+3H2(g)→W(s)+6HCl(g), tungsten coatings were deposited on iron substrates (SS41, 10×13×3mm) at 700°C under flow rates of 30mL/min of argon and 100mL/min of hydrogen. A homogeneous layer was deposited at 6g/h of WCl6 vapor, growing to a thickness of about 20μm in 60min. The substrates were then heated at 1150°C for 30min to improve adhesion of the tungsten. The compound Fe7W6 was found to form between the tungsten coating and the iron substrate. The Vickers hardness of the tungsten layer was 400-500.
(2) SiC coatings on tungsten. Using CVD reaction Si(CH3)Cl3(g)→SiC(s)+3HCl(g), SiC coatings were deposited on tungsten substrates (10×10×0.2mm) for 30min at 1150°C under flow rates of 1.4×10-3mol/min of Si(CH3)Cl3 and 100mL/min of hydrogen. The maximum thickness of the SiC layer was about 25μm. The Vickers hardness of the SiC layer was 3000-3500. The SiC layer revealed excellent resistance to corrosion in a fused salt of NaOH-KOH (50/50mol%) at 300°C. The silicon and carbon appeared to form a solid solution with tungsten at the interface.
(3) SiC coating on tungsten-coated iron. Based on the results of (1) and (2), SiC coatings were deposited on tungsten-coated iron substrates to a maximum thickness of 85μm.
