## 2 Materials and Methods
### Experimental Methods
#### 2.2.4 Organizational Structure and Performance Test  
In this study, a ZEISS EVO 15 scanning electron microscope (SEM) (Carl Zeiss AG, Oberkochen, Germany) was used to characterize the surface morphology and cross-section bonding of the ceramic coatings; a BRUKER D2 X-ray diffractometer (XRD) (Bruker Corporation, Manning Park Billerica, MA, USA) was used to analyze the physical composition of the coatings; and a J-2000 contact angle meter (Beijing Zhongyi Kexin Technology Co., Ltd, Beijing, China) was used to determine the rate of diffusion of the water traces on the surface of the coatings in order to assess the densification. Coating Bonding Strength Test: The bonding strength of the coating itself and the shear strength between the coating and the substrate were determined by the lap method using an electronic tensile tester. As shown in Figure 3, Figure 3a illustrates the lap joint structure of the ceramic coated specimens, where 1 and 3 are metal samples with coatings, and 2 is epoxy resin adhesive; and in Figure 3b, both 1 and 2 are metal substrates. The specimens were cured after bonding and subjected to tensile testing on an electronic tensile testing machine to determine the shear strength, a value that can be used to characterize the bonding properties between the coating and the substrate, as well as the coating itself. The bond strength is calculated by the following Equation (1) [45]:  
\[\tau=\mathrm{P}/(\mathrm{B}*\mathrm{L}) \tag{1}\]  
where \(\tau\) is the bond strength of the specimen, MPa; P is the maximum load of the specimen for shear damage, N; B is the width of the specimen lap surface, mm; L is the length of the specimen lap surface, mm. The abrasion resistance test was carried out by M-2000 friction and wear tester (Zhongte Testing Machine Co., Ltd, Jinan, China), and the uncoated Q235 steel (China Baowu Iron & Steel Group Limited, Shanghai, China)substrate was used as the comparison benchmark. The test parameters were set as follows: load 15 N, rotational speed 100 rpm, test time 30 min. SiC grinding wheels were used for the friction side, and the wear radius was 35 mm. At the end of the experiment, the abraded specimens were removed after natural cooling and cleaned with acetone and blown dry by a hair dryer. The change in mass of the specimens before and after abrasion was measured by means of a precision balance, and the test was repeated three times for each sample, and the average value of the abrasion per unit area was calculated. The wear resistance of the material was characterized by the relative abrasion resistance (\(\varepsilon\)), which was calculated by the following Equation (2):  
\[\varepsilon=\mathrm{M_{0}/M_{n}} \tag{2}\]  
where \(\varepsilon\) is the relative wear resistance; M\({}_{0}\) is the amount of wear of the standard specimen; M\({}_{n}\) is the amount of wear of the tested specimen. The larger the relative wear resistance \(\varepsilon\), the better the wear resistance of the material. HXS 1,/0000A Vickers microhardness tester (Beijing TIME High Technology Co. Ltd. Beijing, China) was used to test the microhardness of ceramic coatings under the following conditions: the test load was 200 g, the loading time was 15 s, and five test values were taken to calculate the average value. Thermal shock resistance testing is used to evaluate the stability of a specimen in an environment of drastic temperature changes. When a coating undergoes alternating hot and cold changes, thermal stresses are generated within it, which may lead to cracking or peeling of the coating if the stresses exceed the coating's tolerance limit. Therefore, the thermal shock resistance test can be used to directly evaluate the bonding performance between the coating and the substrate. The failure of the coating is determined by observing whether the coating surface shows initial cracks, local buckling, or more than one-third of the macroscopic peeling.