Abstract: In order to improve the bond strength of the first interface cementing，the silica matrix ceramic coatings were prepared
on N80 steel substrates as transitional coating between casing steels and well cement by thermochemical reaction method. The
characteristics of the interfacial microstructures and bonding behavior were investigated by the structure，morphology and
binding forces of the samples with XRD，SEM，Stereomicroscope and Scratch Tester. The results show that the interface of
ceranic coating and cement created the new phase MgAl2O4 and Ca54MgAl2Si16O90，respectively. The critical adhesion between
the ceranic coating and the steel matrix is 40 N or so，and the preparation of the ceranic coating is helpful to improve the bonding
strength on the first interface.

Key words: the first interface cementing, cementing strength, thermochemical reaction, silica matrix ceramic coatings, wellcement