Model of the alphinising coating crystallisation on iron alloys

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

Abstrakty

EN

The study presents a hypothetical model of crystallisation of the alphinising coating produced on iron alloys by immersion in the bath of silumin. Basing on a wide-range of experiments and investigations, the effect of the type of inserted material ("armco" iron, C45 steel, grey cast iron and nodular graphite cast iron) and of the technological regime of the alphinising process (chemical composition of silumin bath, its temperature, the time of holding an insert in the bath, and the insert surface roughness height "Rz") on the coating structure was determined. The type of the coating structure was established by metallographic examinations carried out by optical microscopy, electron transmission microsopy and scanning electron microscopy, using additionally an X-ray microanalyser and X-ray diffraction patterns. The results of these investigations were described in [1-7]. Basing on the obtained results, a probable model of the crystallisation of an alphinising coating on iron alloys, produced by immersion in the alphinising bath, was developed. It has been stated that, most probably, the alphinising process begins when the insert reaches its contact temperature "ts".. Since that moment, due to the wetting process and convection movement of bath around the insert surface, an intense process of the dissolution starts. A reactive diffusion of the atoms of Fe and Si from the insert to the bath and of the atoms of Al and Si from the bath to the insert takes place. An intermetallic Al3Fe phase is crystallising on the steel, while on the cast iron, a silicon carbide Fe4CSi is growing, probably due to carbon diffusion from graphite. Then, on the steel, as an effect of the peritectic reaction, are successively crystallising the phases of Al12Fe3Si2 and Al9Fe3Si2. The Al3Fe phase probably crystallises on the cast iron to be transformed later, due to peritectic reaction, into an Al12Fe3Si2 phase on which the Al9Fe3Si2 phase will be growing. When the insert is taken out from the bath, on the Al9Fe3Si2 phase are crystallising the phase constituents present in the silu-min bath. It has been proved that the process of crystallisation of the alphinising coating and its thickness are also affected by the roughness height "Rz". There is a critical value of "Rz", different for the steel and cast iron, up to which the thickness of the coating is growing, and which - when exceeded - makes the coating thickness decrease.

Słowa kluczowe

EN

innovative casting technologies; iron alloys; silumins; alphinising; layered castings; X-ray microanalysis

PL

innowacyjne technologie odlewnicze; stopy żelaza; siluminy; odlewy warstwowe; mikroanaliza rentgenowska

• Wydawca: Komisja Odlewnictwa Polskiej Akademii Nauk Oddział w Katowicach
• Czasopismo: Archives of Foundry Engineering
• Rocznik: 2007
• Tom: Vol. 7, iss. 3
• Strony: 123--128
• Opis fizyczny: Bibliogr. 10 poz., rys., wykr.

Twórcy

autor

Pietrowski S.

autor

Szymczak T.

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

Bibliografia

• [1] S. Pietrowski, Structure of alfinizing layer on the gray cast iron, Archiwum Odlewnictwa, nr 11, 2004.
• [2] S. Pietrowski, T. Szymczak, The structure of Al-Si immers-ing coatings on iron alloys, Archiwum Odlewnictwa, nr 12, 2004.
• [3] S. Pietrowski, T. Szymczak, The structure of connection of alphinizing coat with silumin, Archiwum Odlewnictwa, nr 14, 2004.
• [4] S. Pietrowski, T. Szymczak, The influence of surface rough-ness on the coating thickness after alphinizing, Archiwum Odlewnictwa, nr 17, 2005.
• [5] S. Pietrowski, T. Szymczak, The influence of selected tech-nological elements on the structure of alphinizing coat on iron alloys, Archiwum Odlewnictwa, nr 19, 2006.
• [6] S. Pietrowski, T. Szymczak, Diffraction research of the alphinizing coat on iron alloys, Archiwum Odlewnictwa, nr 22, 2006.
• [7] S. Pietrowski, T. Szymczak, Crystallization model of layered cast through the alphinizing coat, Inżynieria Materiałowa, nr 5, 2006, 1178-1183.
• [8] J. C. Viala, M. Peronnet, F. Barbeau, F. Bosselet, J. Bouix, Interface chemistry in aluminum alloy casting reinforced with iron base inserts, Composites, nr A33, 2002.
• [9] P. Nowak, Model research of the formiry of the structure and preperties of the transition zone in layered castings, PhD thesis, Politechnika Śląska, Katowice, 2005 (in Polish).
• [10] 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, Projekt Celowy, nr 6 T08 2003 C/06096.