Corrosion Failure Mechanism of NiCoCrAlY/AlSiY Composite Coatings in Alternating High and Low Temperature Marine Environments
To investigate the corrosion damage and degradation mechanism of NiCoCrAlY/AlSiY composite coatings in alternating high and low temperature marine environments,the corrosion damage behavior of NiCoCrAlY/AlSiY composite coatings was studied by designing the alterna-ting high and low temperature oxidation and high temperature oxidation-acidic salt spray alternating tests.Results showed that after 50 cycles of alternating high and low temperature oxidation at 750 ℃,the coating underwent oxidative erosion in the oxidation test,but the integrity of the surface structure was not damaged.After the experiment,the weight of the alloy increased by only 3.87 mg/cm2,indicating that the coating ef-fectively inhibited the diffusion of oxygen into the interior and prevented the substrate from oxidative attack.During the 50 cycles of alternating high temperature oxidation and acidic salt spray tests,the NiCoCrAlY/AlSiY composite coating experienced severe corrosion degradation,and the alloy weight increased to as high as 13.52 mg/cm2 by the end of the test.Due to long-term salt spray erosion,the oxide layer structure weakened,leading to surface loosening,the formation of corrosion pits,and even peeling.As the number of alternating cycles of high tempera-ture oxidation-acidic salt spray increased,the critical reaction causing coating damage shifted from oxidative erosion to thermal corrosion.The chlorine,generated from the eutectic reaction of the mixed salt,acted as a catalytic carrier and accelerated the growth of oxidation products,demonstrating that the NiCoCrAlY/AlSiY composite coatings had weak corrosion resistance under alternating high temperature oxidation-acidic salt spray environments.
NiCoCrAlY/AlSiY composite coatingmarine environmenthigh and low temperature oxidation alternationhigh-temperature oxi-dation-acidic salt spray alternation
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