Thermal Stability and Mechanical Properties for Ceramic Composite Films Coated on Steel by Wet Process

Abstract

ᛘᗕǺȗș̥ኑˀǺΰ⓯ǦǮ⓹۰ɃɱɧɋȷℋǽᡡયමǷᑿ፦ᣀමૅୖ᰾̘ɿәቆવɿɖᖅໞֳଉ ɿᆎᨀ౯Ԅଉ ଉ ɿଏԆֳଉ ɿ୮ᚊ Iଉ ఎগકগકрἕ۰ᥴకકಊᢼᥴకકଗფࢫ816-8580 ᱨ᭔ᆎᅠలᆎᅠӸ 6-1 ଉఎগકগકрἕ۰ᥴకકᮾ᳣рᢼᲇકȤϘࢫ816-8580 ᱨ᭔ᆎᅠలᆎᅠӸ 6-1 ଉ ଉ ሱBAHAM ཪᮾࢫ150-6019 ኇ̸ȩগᨀٚኇ‫ؤ‬ŋ 2-3-6-201A ceramic coating slurry was designed, which suspended or dissolved ceramic components silica, titania, alumina and kaolinite and glass-forming components alkali silicates and soda ash in water. SiO 2 -Al 2 O 3 -TiO 2 based composite films about 100 mm thick were deposited on a steel plate by coating the slurry with a brush, followed by drying and calcination. The ceramic coatings obtained under proper conditions were found to exhibit excellent stability over a wide range of temperature. As evaluated by copper electrodeposition method, through-holes were present in the coatings calcined at 700c C or below, while they were eliminated completely after calcination at 1100c C in N 2 . Vickers hardness of the coatings increased with increasing calcination temperature, while adhesive strength went through a sharp maximum at 800c C.

Addition of Alkali Silicate to Grain Size-Controlled Ceramic Coatings for Dense Film

“…Previously we reported that the ceramic grains coagulated together more heavily to give smooth and less porous surface morphology, when the addition of glass-forming-components to the non-milled coating increaced. 15,16 Composition ratio for H-1 coating nonmilled was decided finally under such deep investigations. However it is turned out that the milled case gives smoother surface effectively.…”

“…The porous nature of the coating pre-calcined at 420c C or calcined at 800c C was obvious from the SEM images, but it was almost impossible to identify the through-holes of the coatings from such observations. Although we previously tried to visualize the through-holes by Cu electrochemical deposition method, 16 the method, when such pores were very small, seemed to be very difficult. In fact, no Cu-deposition was observed in the H-4b, H-5b and H-6b coatings.…”

“…by a wet process. 15 The ceramic composite film deposited on steel consists of several inorganic materials Al 2 O 3 , SiO 2 , TiO 2 etc.. The ceramic composite film exhibited fairly good adhesion strength and thermal stability in air at temperatures below 600c C. However, the film was spalled in pieces at 700c C and above, because of the oxidation of the steel plate through through-holes in ceramic film.…”

“…Previously we tried to optimize the alkaline silicate component in the ceramic slurry. 16 The optimization gave results that the number of through-holes of the coating decreased drastically with increasing amount of alkali silicates, and that the resistance of the coating to corrosion in 1 moll HCl solution was improved. This investigation should be continued to make progress in the properties.…”