The corrosion behavior of Super304H,HR3C and related aluminized coatings under K_(2)SO_(4)+Na_(2)SO_(4)(mass ratio=1:1)and K_(2)SO_(4)+Na_(2)SO_(4)+KCl(45:45:10)deposits in a mixed gas of 0.5SO_(2)–4O_(2)–20H_(2)O-7...The corrosion behavior of Super304H,HR3C and related aluminized coatings under K_(2)SO_(4)+Na_(2)SO_(4)(mass ratio=1:1)and K_(2)SO_(4)+Na_(2)SO_(4)+KCl(45:45:10)deposits in a mixed gas of 0.5SO_(2)–4O_(2)–20H_(2)O-75.5CO_(2)(vol.%)at 700℃were studied.Super304H undergoes severe corrosion under both deposits,the addition of KCl did not significantly accelerate the corrosion process but resulted in an extremely porous and thickness-doubled scale.While HR3C with higher Cr content shows excellent corrosion resistance in Cl free environment due to the formation of dense Cr_(2)O_(3).Due to the involvement of Cl,HR3C can no longer resist the corrosion of the salts.The corrosion depth increases by two orders of magnitude and becomes as severe as Super304H.Aluminizing significantly improved the corrosion resistance of the alloys on account ofα-Al_(2)O_(3)formation by a new mechanism.The addition of KCl had little effect on this mechanism and only increased the thickness of the corrosion products slightly.展开更多
Aluminized coating was prepared on K452 superalloy by chemical vapor deposition(CVD)technique.The oxidation/corrosion behavior of alloy and coating were investigated at 750℃in air,air with solid NaCl deposit and mois...Aluminized coating was prepared on K452 superalloy by chemical vapor deposition(CVD)technique.The oxidation/corrosion behavior of alloy and coating were investigated at 750℃in air,air with solid NaCl deposit and moist air with solid NaCl deposit,respectively.The microstructure and composition of samples were characterized by SEM/EDS and XRD techniques.The results demonstrated that aluminized coating exhibited better oxidation/corrosion resistance than K452 alloy in the three environments above.And the main oxidation and corrosion products of alloy were Cr_(2)O_(3)and NiO,respectively.This indicated that Ni participated in the corrosion process due to the depletion of Cr during accelerated corrosion.Therefore,the established corrosion scale was non-protective,which could not protect underlying alloy from accelerated corrosion.Contrarily,the main oxidation and corrosion products of coating were protective Al_(2)O_(3),which acted as a barrier to separate coating from NaCl and oxygen,interrupting the self-sustainable accelerated corrosion.Additionally,the presence of water vapor was beneficial in reducing the spallation of corrosion products within a short time.The mechanisms of K452 alloy and aluminized coating in the three environments above were discussed in detail.展开更多
Aluminizing coating and aluminizing-dispersed Y 2O 3 composite coating were prepared on 20 steel specimens by pulsed spark technique, which exhibited a micro-crystallized structure with grain size in the range of se...Aluminizing coating and aluminizing-dispersed Y 2O 3 composite coating were prepared on 20 steel specimens by pulsed spark technique, which exhibited a micro-crystallized structure with grain size in the range of several ten to several hundred nanometers. It is shown that, after oxidation at 600 ℃ in air for 100 h, these two kinds of coatings have excellent resistance to high temperature oxidation and scale spallation, and the aluminizing-dispersed Y 2O 3 composite coating has even better property than the aluminizing coating. AFM, SEM, EDS and XRD were applied to analyze the surface morphology, composition and phases structure of these coatings and the oxide scale formed in oxidation. The mechanism for these coatings that how to enhance the oxidation resistance and scale spallation resistance was discussed by considering the factors, such as Al concentration on the selective oxidation of Fe-Al alloy, the effect of micro-crystallization, reactive element effect (REE) caused by dispersed Y 2O 3, etc.展开更多
A Cr-modified aluminide coating is prepared on a Ni-based superalloy using arc ion plating and subsequent pack cementation aluminizing.Hot corrosion behavior of the Cr-modified aluminide coating exposed to molten Na2S...A Cr-modified aluminide coating is prepared on a Ni-based superalloy using arc ion plating and subsequent pack cementation aluminizing.Hot corrosion behavior of the Cr-modified aluminide coating exposed to molten Na2SO4/K2SO4（3：1） or Na2SO4/NaCl（3：1） salts at 900 °C in static air are evaluated as well as the aluminide coating.The results indicate that compared with the aluminide coating,the anti-corrosion properties of the Cr-modified aluminide coating in the both salts are improved,which should be attributed to the beneficial effect of the Cr in the coating.The corrosion mechanism of the Cr-modified aluminide coating,especially the role of Cr in the mixture salt corrosion,is discussed.展开更多
基金supported by the Liaoning Revitalization Talents Program (XLYC2203133)the Fundamental Research Funds for the Central Universities (N2302018)the Ningbo Yuyao City Science and Technology Plan Project (2023J03010010)
文摘The corrosion behavior of Super304H,HR3C and related aluminized coatings under K_(2)SO_(4)+Na_(2)SO_(4)(mass ratio=1:1)and K_(2)SO_(4)+Na_(2)SO_(4)+KCl(45:45:10)deposits in a mixed gas of 0.5SO_(2)–4O_(2)–20H_(2)O-75.5CO_(2)(vol.%)at 700℃were studied.Super304H undergoes severe corrosion under both deposits,the addition of KCl did not significantly accelerate the corrosion process but resulted in an extremely porous and thickness-doubled scale.While HR3C with higher Cr content shows excellent corrosion resistance in Cl free environment due to the formation of dense Cr_(2)O_(3).Due to the involvement of Cl,HR3C can no longer resist the corrosion of the salts.The corrosion depth increases by two orders of magnitude and becomes as severe as Super304H.Aluminizing significantly improved the corrosion resistance of the alloys on account ofα-Al_(2)O_(3)formation by a new mechanism.The addition of KCl had little effect on this mechanism and only increased the thickness of the corrosion products slightly.
基金financially supported by the National Key R&D Program of China(No.2020YFB2010404)
文摘Aluminized coating was prepared on K452 superalloy by chemical vapor deposition(CVD)technique.The oxidation/corrosion behavior of alloy and coating were investigated at 750℃in air,air with solid NaCl deposit and moist air with solid NaCl deposit,respectively.The microstructure and composition of samples were characterized by SEM/EDS and XRD techniques.The results demonstrated that aluminized coating exhibited better oxidation/corrosion resistance than K452 alloy in the three environments above.And the main oxidation and corrosion products of alloy were Cr_(2)O_(3)and NiO,respectively.This indicated that Ni participated in the corrosion process due to the depletion of Cr during accelerated corrosion.Therefore,the established corrosion scale was non-protective,which could not protect underlying alloy from accelerated corrosion.Contrarily,the main oxidation and corrosion products of coating were protective Al_(2)O_(3),which acted as a barrier to separate coating from NaCl and oxygen,interrupting the self-sustainable accelerated corrosion.Additionally,the presence of water vapor was beneficial in reducing the spallation of corrosion products within a short time.The mechanisms of K452 alloy and aluminized coating in the three environments above were discussed in detail.
文摘Aluminizing coating and aluminizing-dispersed Y 2O 3 composite coating were prepared on 20 steel specimens by pulsed spark technique, which exhibited a micro-crystallized structure with grain size in the range of several ten to several hundred nanometers. It is shown that, after oxidation at 600 ℃ in air for 100 h, these two kinds of coatings have excellent resistance to high temperature oxidation and scale spallation, and the aluminizing-dispersed Y 2O 3 composite coating has even better property than the aluminizing coating. AFM, SEM, EDS and XRD were applied to analyze the surface morphology, composition and phases structure of these coatings and the oxide scale formed in oxidation. The mechanism for these coatings that how to enhance the oxidation resistance and scale spallation resistance was discussed by considering the factors, such as Al concentration on the selective oxidation of Fe-Al alloy, the effect of micro-crystallization, reactive element effect (REE) caused by dispersed Y 2O 3, etc.
基金financially supported by the National Natural Science Foundation of China (No.51001106)National Basic Research Program of China (No.2012CB625100)
文摘A Cr-modified aluminide coating is prepared on a Ni-based superalloy using arc ion plating and subsequent pack cementation aluminizing.Hot corrosion behavior of the Cr-modified aluminide coating exposed to molten Na2SO4/K2SO4（3：1） or Na2SO4/NaCl（3：1） salts at 900 °C in static air are evaluated as well as the aluminide coating.The results indicate that compared with the aluminide coating,the anti-corrosion properties of the Cr-modified aluminide coating in the both salts are improved,which should be attributed to the beneficial effect of the Cr in the coating.The corrosion mechanism of the Cr-modified aluminide coating,especially the role of Cr in the mixture salt corrosion,is discussed.
