The Research of Mechanism and Preparation of High Temperature Resistant Oxidation Coating on Titanium Sponge Reactor
Yu Xin
CNKI
Abstract
The sponge titanium reactor often works in hot and humid environment, so it is prone to be oxidated. The reactor used in building material industry all has been oxidated in different degrees when it works more than one year. The reactor will be completely destroyed only after four or five years if the oxidation is serious. The high temperature oxidation of the reactor has not only a tremendous waste of resources but also a serious effect on the safety of production. Therefore the law of metallic high temperature oxidation was studied and mastered. The theoretical knowledge in this area was used to reduce or inhibit the high temperature oxidation reaction, which is bound to decrease or retrieve the losses caused by oxidation and promote the development of related fields.
In the experiment, an arc spraying method was used to prepare high temperature oxidation resistant coating. The Al coating, 45CT coating and their composite coatings were sprayed on Q235 steel, and then the sealing agent was used for sealing treatment on coating. The experimental comparison shows that the coating with thickness of 0.6mm has the best resistant oxidation properties among the coating with thickness of 0.2mm, 0.4mm,0.6mm, 0.8mm and 1.0mm under the same condition. The high temperature oxidation experiments for three kinds of coatings with thickness of 0.6mm were performed at 780℃and 980℃, respectively. In addition, the adding weight of the coating was measured. The coatings were observed and analyzed with such modern analysis means as XRD, SEM and EDS, and the resistant oxidation mechanism of the coatings was studied and discussed.
With the observation and data analysis, the following conclusions can be obtained:The three kinds of coatings all have high temperature oxidation resistance, among which the 45CT coating has the best high temperature oxidation resistance. The high temperature oxidation resistance of the Al coating was lower than that of the 45CT coating, and the high temperature oxidation resistance of the composite coating is the worst. After high temperature oxidation, the oxide films of Al and composite coatings fall off in some degree,and the coating microstructure is loose, so the protection action of the coatings is weakened. The 45CT coating has complete surface, and the Cr2O3 coating exhibits excellent high temperature oxidation resistance which can protect the substrate from oxidation. A transition layer exists in the combination area between each kind of coating and the substrate. The transition layer can not only improve the bonding strength between the coatings and the substrate but also restrain the element diffusion, which can further protect the substrate.
Key Words: arc spraying, high temperature resistant oxidation, oxidation mechanism, transition layer
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