Studies of composite surface layer structure on castings of iron alloys
Jan Szajnar, Piotr Wróbel, Tomasz Wróbel
Quarterly No. 3, 2009 pages 282-285
DOI:
keywords: composite surface layer, structure
abstract The paper presents a method of usable properties of surface layers improvement of cast carbon steel, by put directly in founding process a composite surface layer on the basis of Fe-Cr-C alloy. Technology of composite surface layer guarantees mainly increase in hardness and aberasive wear resistance of cast steel and cast iron castings on machine elements. This technology can be competition for generally applied welding technology (surfacing by welding and thermal spraying). In earlier studies authors showed, that exist possibility of control of thickness, hardness and aberasive wear resistance of type metal-mineral of composite surface layer by suitable selection of parameters i.e. thickness of composite insert, pouring temperature and solidification modulus of casting. Composite layers with large thickness are results from use of larger thickness of composite insert, higher pouring temperature and larger thickness of casting wall i.e. larger solidification modulus. Thicker layers have smaller hardness than thin layers. It result from larger diluting of alloying constituents after long time of diffusion. Moreover obtained thickness of composite layers are proper for assurance of suitable time of castings exploitation. The industrial application of composite surface layers technology among other things take in founding of cast steel slide bush for combined cutter loader, in which moves a arm of head to mining of hard coal, in founding of aberasive wear resistant skid and in founding of cast iron ingot moulds, which have high thermal shock resistance. Whereas in particular the paper presents a part of structure studies, which were made with use of light microscope Nikon EPIPHOT-TME, scanning electron microscope Inspect F with EDS system and X-ray diffractometer Panalytical RTG XPertPro. On the basis of results was affirmed that structure of composite surface layer contains matrix i.e. alloy ferrite and carbides mainly M7C3. Acicular carbides and carbide eutectic were distinguished. Moreover was observed, that increase of casting mass results in increase in range of selected elements diffusion for example carbon and chromium. This is very important for created transition zone, which strongly influences on quality of joint between layer and base casting.