Preparation of silicate enamel coating by plasma spraying and study on its thermal cycling behavior
[Introduction]The failure behavior of silicate enamel coating in the process of hot/cold cycling has received little attention.[Method]A agglomerated and sintered multi-component silicate powder suitable for atmospheric plasma spraying was prepared with SiO2,Al2O3,Na2CO3,and CaO by the combination of spray granulation and sintering,and then used to fabricate a silicate coating on the surface of 12CrMoV alloy steel by atmospheric plasma spraying technology.The microstructure and thermal cycling behavior of the coating at 700 ℃ were studied.[Result]The agglomerated and sintered silicate powder is spherical with a particle size ranging from 20 to 60 μm.The plasma-sprayed silicate coating presents obvious layer stacking deposition,and its surface is relatively rough.Although there are a certain number of closed pores inside,the whole coating is relatively compact.The coating is composed of not only a certain amount of amorphous phases,but also some crystalline phases such as SiO2,Al2SiO5,and Ca2MgSi2O7.The plasma-sprayed silicate coating failed due to partial brittle spalling after 145 cycles of thermal shock at 700 ℃ under water quenching.[Conclusion]The failure of the coating may be due to the partial oxidation of the metal matrix,the decomposition of crystal phases,and the thermal stress caused by the alternating heat and cold cycle.
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