Fabrication and wear properties of Al2O3-SiC ceramic coatings using aluminum phosphate as binder

Refractory and wear-resistant Al2O3-SiC ceramic coatings have been fabricated on A3 steel using abrasive ceramics (Al2O3, SiC), aluminum phosphate binder (inorganic binder), and aluminate (Al2O3 · CaO) as starting materials. The Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques are used to investigate the chemical compositions of the in-house synthesized aluminum phosphate binder and the morphologies of the fabricated ceramic coatings after abrasion test. The XRD results indicate that monoaluminium phosphate (Al(H2PO4)3) is the most effective binding phase in aluminum phosphate binder, and that aluminum phosphate binder at high temperatures is a mixture of several phases. It is also found that the addition amount of the stabilizer (oxalic acid) has remarkable effect on the storage life of aluminum phosphate binder. The wear test results show that the wear resistance of the A3 steel covered with Al2O3-SiC ceramic coatings is about two times higher than that of the uncoated A3 steel. The results also indicate that the wear properties of Al2O3-SiC ceramic coatings are dependent on fabrication conditions, such as the weight ratio of ceramics to the binder (RCB), the particle size distribution of ceramics, the density of the aluminum phosphate binder, and the Al/P atomic ratio in the aluminum phosphate binder. The optimal fabrication conditions for achieving good wear resistance of Al2O3-SiC ceramic coatings are suggested based on the above results.