Agnieszka Kochmańska

Hot Corrosion Resistance Properties of Al-Si Coatings Obtained by Slurry Method

This paper presents the results of research on aluminide protective coatings manufactured on hightemperature creep resistant cast steel. The main purpose of these coatings is protection against the high temperature corrosion, at carburizing and oxidizing potential atmosphere. Coatings were obtained on cast steel type GXNiCrSi 3018 by slurry cementation in air atmosphere. The tests of carburizing and oxidizing were carried out. The structure of the coatings before and after carburizing and oxidizing is described in the present paper. The chemical composition, thickness and microstructure of coatings were determined. These coatings could protect equipment against hot corrosion at carburizing and oxidizing atmosphere and have thermal shocks resistance.

Microstructure of aluminide coatings on Ti6Al4V alloy produced by the slurry method with inorganic binder

Abstract Slurry aluminide coatings were produced on Ti-based alloy Ti6Al4V in an argon atmosphere. A slurry with a newly-developed composition was applied, consisting of: powders of aluminium and silicon, a fused mixture of salts as an activator and a water solution of a soluble glass as an inorganic binder. The coating production parameters were varied: annealing temperatures of 900, 1000 and 1100°C were used for annealing times of 2, 4 and 6 h. The microstructure, chemical composition and phase composition of the coatings were studied. The correlation between the technological parameters and the coating thickness was also determined. The obtained coatings have a multilayered structure with a phase layout that is desirable from the viewpoint of mechanical and corrosion resistance performance: aluminium-rich phases on the surface and titanium-rich phases near the substrate.

Microstructure of Al-Si Slurry Coatings on Austenitic High-Temperature Creep Resisting Cast Steel

This paper presents the results of microstructural examinations on slurry aluminide coatings using scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. Aluminide coatings were produced in air atmosphere on austenitic high-temperature creep resisting cast steel. The function of aluminide coatings is the protection of the equipment components against the high-temperature corrosion in a carburising atmosphere under thermal shock conditions. The obtained coatings had a multilayered structure composed of intermetallic compounds. The composition of newly developed slurry was powders of aluminium and silicon; NaCl, KCl, and NaF halide salts; and a water solution of a soluble glass as an inorganic binder. The application of the inorganic binder in the slurry allowed to produce the coatings in one single step without additional annealing at an intermediate temperature as it is when applied organic binder. The coatings were formed on both: the ground surface and on the raw cast surface. The main technological parameters were temperature (732–1068°C) and time of annealing (3.3–11.7 h) and the Al/Si ratio (4–14) in the slurry. The rotatable design was used to evaluate the effect of the production parameters on the coatings thickness. The correlation between the technological parameters and the coating structure was determined.

The utilization of the mesoporous Ti-SBA-15 catalyst in the epoxidation of allyl alcohol to glycidol and diglycidyl ether in the water medium

Abstract This work presents the studies on the optimization the process of allyl alcohol epoxidation over the Ti-SBA-15 catalyst. The optimization was carried out in an aqueous medium, wherein water was introduced into the reaction medium with an oxidizing agent (30 wt% aqueous solution of hydrogen peroxide) and it was formed in the reaction medium during the processes. The main investigated technological parameters were: the temperature, the molar ratio of allyl alcohol/hydrogen peroxide, the catalyst content and the reaction time. The main functions the process were: the selectivity of transformation to glycidol in relation to allyl alcohol consumed, the selectivity of transformation to diglycidyl ether in relation to allyl alcohol consumed, the conversion of allyl alcohol and the selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed. The analysis of the layer drawings showed that in water solution it is best to conduct allyl alcohol epoxidation in direction of glycidol (selectivity of glycidol 54 mol%) at: the temperature of 10–17°C, the molar ratio of reactants 0.5–1.9, the catalyst content 2.9–4.0 wt%, the reaction time 2.7–3.0 h and in direction of diglycidyl ether (selectivity of diglycidyl ether 16 mol%) at: the temperature of 18–33°C, the molar ratio of reactants 0.9–1.65, the catalyst content 2.0–3.4 wt%, the reaction time 1.7–2.6 h. The presented method allows to obtain two very valuable intermediates for the organic industry.

Aluminide Protective Coatings Obtained by Slurry Method

The slurry aluminide coatings are produced on the three kind of substrates: hightemperature creep resistant cast steel, titanium alloy and nickel alloy. The slurry as active mixture containing aluminium and silicon powders, an activator and an inorganic binder. The coating were obtained by annealed in air atmosphere. The structure of these coatings is two zonal and depend on the type of substrate and technological parameters of producing.

Structure of Intermetallic Al–Si Coating on Inconel 617

Nickel superalloy was coated by aluminide coatings by the slurry method. The slurry as active mixture containing aluminium and silicon powders, an activator and a binder. The coating were obtained by annealed in argon atmosphere. The structure of these coatings is two zonal and depends on time and temperature of producing. The phase composition was determined using following techniques: scanning electron microscopy (SEM) equipped with Xray microanalysis (EDS) combined with electron backscatter diffraction (EBSD) and Xray diffraction (XRD).

High-Temperature Diffusion Barrier for Ni-Cr Cast Steel

The study describes aluminium-silicon protective coatings produced by the slurry cementation process on a substrate of creep-resistant Ni-Cr cast steel. The mechanism of the coating growth on a substrate was examined and the effect of annealing time and temperature on total thickness of the coatings and on the thickness of the individual zones was analyzed. The coating structure is composed of two zones. In the external zone, elements like Al, Ni and Fe are concentrated, forming intermetallic phases of an Al(Ni,Fe) type, while the internal zone contains an (Fe,Cr,Si) solution. The internal zone formed in a sub-surface layer of the substrate has hardness values intermediate between the hardness of the substrate and that of the external layer.