Study On The Preparation Of The Anti-oxidation Protective Coating Based On Attapulgite At High-temperature And Its Application

Workpiece heated at high-temperature usually reacts with oxidizing gases, e.g. CO₂, O₂ and H₂O, etc, leading remarkable oxidization on the surface of the workpiece. It will not only waste the steel materials, but also decrease mechanical properties and workpiece quality. Furthermore, it will cost too much labor and money to remove the oxidation -decarbonization-layer. The natural selection of protective coating technique for solving these questions is determined by a combination of most favorable characteristics including a better protective ability, a simple preparative technics, no pollution and lower unit cost.Attapulgite contains SiO₂, Al₂O₃, and MgO, which are indispensable typical ingredients in high-temperature antioxidation coating. Attapulgite also has good plasticity, flowability, chemical inertness and thermal stability. Furthermore, it is abundant in resources. After drying, it not easy to crack, its shrinkage is small. Based on the above mentioned points, attapulgite can be exploited to the protective coating with anti-oxidation at high-temperature of steel.In this thesis, thermal film shield and oxidoreduction protective mechanism were adopted as the principles of protective coating. The optimal formula of protective coating with anti-oxidation at high-temperature for 60Si2Mn spring steel and GCr15 bearing steel was optimized by orthogonal experiment method, with attapulgite as the main raw material, adding an appropriate amount of auxiliary materials. Effect to coating by the heating temperature and holding time were analysed. The ability of the coating to isolate oxygen was tested. Comparisons between ATP coating and 202 coating were made from protective efficacy and economical efficiency. The changings of decarburization thickness were investigated by metallographic method. Then verified the accuracy of experimental datas in theory, and analyzed the protective mechanism of coating.The results show that this coating can significantly reduce the oxidation loss of 60Si2Mn spring steel and GCr15 bearing steel in heat-treatment from 800℃to 1200℃. The effectiveness of the coating is equivalent to 202 coating, and moreover, it can save on expenses by 62.46%, when protect the same area of steel.