Effect of silicon concentration in bath on the structure and thickness of grey cast iron coating after alphinising

• Autorzy: Pietrowski S. , Szymczak T.
• Języki publikacji: EN

Abstrakty

EN

Purpose: This paper presents the results of studies on the effect of silicon content in alphinising bath on the thickness of diffusion layer "g1" and of coating "g" produced by immersion on the grey cast iron, grade EN-GJL-250. The temperature of alphinising bath was 750 ± 5°C, and the time of holding the cast iron insert was ζ=180s. Design/methodology/approach: It has been proved that in the bath of commercially pure aluminium and of AlSi1,5 alloy, the diffusion layer and coating produced on grey cast iron are of the highest thickness, comprised in a range of g1=40 ÷ 50µm and g = 220 ÷ 230µm., respectively. The diffusion layer produced in these baths is characterised by a compact, columnar structure of the Al3Fe phase. Findings: An increase in silicon concentration in the alphinising bath to about 11% changes the structure of diffusion layer into the faceted one and makes other phases appear as well. Right on the surface of the cast iron insert, the Fe4CSi carbide is present, followed by the Al12Fe3Si2 phase, on which the Al9Fe3Si2 phase is superimposed. Raising further silicon concentration in bath to a level well above 11% Si, i.e. to about 17% Si, does not change the phase constitution of the diffusion layer. What it causes is only a fragmentation (breaking of continuity) of the layer, thus making it useless in the process of producing a layered casting. An increase in silicon concentration in the alphinising bath in a range of 7 ÷ 17% Si reduces the thickness of diffusion layer in a range of g1=38 ÷ 22µm and that of coating in a range of g=155 ÷ 92 µm. It is supposed that the decrease in thickness of the diffusion layer and of coating with the increasing concentration of silicon in alphinising bath is due to a reduced rate of the reactive diffusion. Originality/value: This is an immediate effect of the enlarged number of silicon atoms and of the presence of the precipitates of primary silicon crystals adhering to the surface of cast iron insert. The reason of occurrence of a monophase structure in the diffusion layer produced in aluminium bath or in bath of AlSi1,5 is the lack of silicon atoms or low concentration of this element in the region of the surface layer dissolved on cast iron insert.

Słowa kluczowe

EN

casting; aluminium; silumins; grey cast iron; alphinising; layered castings; X-ray microanalysis

PL

odlew; aluminium; siluminy; żeliwo szare; warstwy odlewów; mikroanaliza rentgenowska

• Wydawca: International OCSCO World Press
• Czasopismo: Archives of Materials Science and Engineering
• Rocznik: 2007
• Tom: Vol. 28, nr 7
• Strony: 437--440
• Opis fizyczny: Bibliogr. 13 poz., il., wykr.

Twórcy

autor

Pietrowski S.

autor

Szymczak T.

• Chair of Materials Engineering and Production Systems, Technical University of Łódź ul. Stefanowskiego 1/15, 90-924 Łódź, Poland,

Bibliografia

• [1] J. C. Viala, M. Peronnet, F. Barbeau, F. Bosselet, J. Bouix, Interface chemistry in aluminum alloy casting reinforced with iron base inserts, Composites A33 2002 234-238.
• [2] P. Nowak, Model research of the formiry of the structure and preperties of the transition zone in layered castings, PhD thesis, Silesian University of Technology, Katowice, 2005 (in Polish).
• [3] S. Pietrowski, The crystalization, structure and properties of piston silumins, Łódź University of Technology Press, 1999 (in Polish).
• [4] S. Pietrowski, Production technology of castings of casing compressors with aluminum alloys with inserted cast iron elements working under conditions of high pressure of the air, helium and the oil, Project 6 T08 2003 C/06096 (in Polish).
• [5] S. Pietrowski, T. Szymczak, The influence of selected technological elements on the structure of alphinizing coat on iron alloys, Archives of Foundry 19 (2006) 1-8 (in Polish).
• [6] S. Pietrowski, T. Szymczak, Crystallization model of layered cast through the alphinizing coat, Materials Engineering 5 (2006) 1178-1183 (in Polish).
• [7] S. Pietrowski, Structure of alfinizing layer on the gray cast iron, Archives of Foundry 11 (2004) 33-38 (in Polish).
• [8] S. Pietrowski, T. Szymczak, The structure of Al-Si immersing coatings on iron alloys, Archives of Foundry 12, (2004) 7-16 (in Polish).
• [9] S. Pietrowski, T. Szymczak, The structure of connection of alphinizing coat with silumin, Archives of Foundry 14, (2004) 23-30 (in Polish).
• [10] S. Pietrowski, T. Szymczak, The influence of surface roughness on the coating thickness after alphinizing, Archives of Foundry 17 (2005) 44-50 (in Polish).
• [11] S. Pietrowski, T. Szymczak, Diffraction research of the alphinizing coat on iron alloys, Archives of Foundry 22, (2006) 22-28 (in Polish).
• [12] C. Podrzucki, Cast iron. The structure, properties, application. ZG STOP, Kraków, 1991 (in Polish).
• [13] S. Pietrowski, Silumins, Łódź University of Technology Press, 2001 (in Polish).