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2 Journal of Achievements in Materials and Manufacturing Engineering

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Oxidation and exhaust gas corrosion resistance of the cobalt base clad layers

Smolenska H.

Journal of Achievements in Materials and Manufacturing Engineering

2008

Vol. 31, nr 2

364-372

Purpose: Purpose of this work is describing the behaviour of the cobalt base cladding layers after treatment in hot air (750° C, 200 hours) and exhaust gases (700° C, two month). Design/methodology/approach: The layers were produced by two cladding, laser and PTA, cladding technique. Cladding was conducted with a high power diode laser HDPL ROFIN SINAR DL 020 and Plasma Transformed Arc method. The layers consisted of three multitracking sublayers. The cobalt base layers were evaluated by microstructure investigations (optical and scanning electron microscope SEM), chemical analysis and micro hardness measurements. Findings: The microstructure of the investigated layers did not change much, neither on the top part nor in the clad/steel interface after treatment in both environments. On the outer surfaces the oxide layers were observed which consisted generally of chromium and iron oxides. The compositions of this scales were reviled by the EDS analyze. The changes in chemical compositions before and after oxidation and after corrosion in exhaust gases in the dendritic regions and micro regions were confirmed by the semi-quantitative chemical analysis (EDS). Neither the oxidation nor exposition for two month in exhaust gases did not influence on the morphology of the clad layers in any region however changes in chemical composition were observed. For both sort of clads the oxide layers were observed on the surface. The proposed layers are resistant for the hot exhausted gases. Research limitations/implications: The future researches should be done on microstructural and kinetic analyze of high temperature corrosion for higher temperature and times of the process. Practical implications: The clad layers, of this composition, were designed as a method to prolong service time for the ship engine exhausted valve and after this investigation the first valve heads with laser clad layer were installed in working ship engine. Originality/value: The chemical composition of the powder was new one. Also using the laser cladding technique for ship engine parts subject of interesting.

The gas corrosion of the cobalt base clad layer at elevated temperature

Smolenska H.

Journal of Achievements in Materials and Manufacturing Engineering

2006

Vol. 18, nr 1-2

235--238

Purpose: Purpose of this paper is to evaluate the microstructural and mechanical properties evolution of the laser and PTA clad layers made of the powder containing cobalt after oxidation in air (750°C, 200 hours) and corrosion in exhaust gases (700°C, two month). Design/methodology/approach: The layers were made by cladding technique. Cladding was conducted with a high power diode laser HDPL ROFIN SINAR DL 020 and Plasma Transformed Arc method. The subsequent tracks were overlapped by 30÷40%. The performance of the hardfaced materials were evaluated by microstructure (optical and scanning electron microscope SEM), chemical analysis and micro hardness measurements. Findings: After heat treatment the microstructure of the clad layers did not change much, neither on the top part nor in the clad/steel interface. However the oxide layer on the surface is observed. The EDS analyze revile the composition of this scale which consisted generally of chromium and iron oxides. The semi-quantitative chemical analysis (EDS) of the dendritic regions and micro regions confirms changes in chemical contents before and after oxidation and after corrosion in exhaust gases. The oxidation at temperature 750°C for 200 hours in air and for two month in exhaust gases did not influence on the morphology of the clad layers neither on the top part nor in the clad/steel interface. However changes in chemical composition were observed. On the surface of both sort of clads the oxide layers were observed. These sorts of layers are resistant for the hot exhausted gases. Research limitations/implications: During the future research kinetic analyze of high temperature corrosion should be done also for different temperature and times of the process. Practical implications: The layers were designed as a method to prolong service time for the ship engine exhausted valve. Originality/value: The chemical composition of the powder was new one. Also using the laser cladding technique for ship engine parts is a subject of interest.