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2 Archives of Foundry Engineering

2 2009

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Efficiency of protective coatings on high creep resistant cast steel

Kochmańska A., Kubicki J.

Archives of Foundry Engineering

2009

Vol. 9, iss. 2

129-132

This paper presents results of research of multilayer aluminium-silicon coatings. Aluminium-silicon coatings were created on high-temperature creep resist cast iron using slurry method in air atmosphere. These coatings protect equipment against hot corrosion in carburizing atmosphere at thermal shocks conditions. Various technological parameters of coatings manufacturing were applied. Main technological parameters were: temperature and time of annealing and Al-Si ratio in the active mixture. The structure of obtained coatings is three-zonal. Phase composition of two external zones ensures protection against carburizing, but these zones are not resistant to cracking. The cracks form as a result of thermal shocks. The internal zone of the coatings situated next to substrate compensates for differences of thermal expansion of the coating and the substrate. The cracks are stopped in the internal zone and do not propagate into the substrate material. Protective efficiency of the coatings at carburizing conditions with thermal shocks was determined. Structure of the coatings before and after carburizing and thermal shocks is described in present paper. Thickness, chemical composition (EDS) and phase composition (XRD) of the coatings are determined. Correlation between the coatings structure and depth of carburized layer was determined.

Aluminide protective coatings on high-temperature creep resistant cast steel

Kubicki J., Kochmańska A.

Archives of Foundry Engineering

2009

Vol. 9, iss. 4

113-124

This paper presents the results of research on aluminide protective coatings manufactured on high-temperature creep resistant cast steel. The main purpose of these coatings is protection against the high temperature corrosion, especially at high carburizing potential atmosphere. Coatings were obtained on cast steel type G-XNiCrSi36-18 with the following methods: pack cementation, paste method, cast method and slurry cementation. The phase composition, thickness and morphology of coatings were determined. Coatings capacity of carbon diffusion inhibition and thermal shocks resistance of coatings were determined with different methods. It was found, that all of the coatings reduce carbon diffusion in different degree and all coatings liable to degradation in consequence cracking and oxidation. Coating life time is mainly dependent on morphology, phase composition and service condition (thermal shocks first of all).