Composition and Structure of Surface Layer in Composite Castings from Gray Cast Iron Formed Using Chromium-Ferroboron Master Alloys

A method for obtaining composite surface-alloyed castings from gray cast iron SCh25 by cavityless casting with the use of master alloys containing chromium and ferroboron deposited as a paste layer on the surfaces of the casting molds is considered. The microstructure and the phase composition of the surface layer and the microhardness of the structural components are determined. Mechanical tests of the cast samples for compression and wear are carried out. Self-propagating high-temperature synthesis is shown to occur between the components of the master alloys deposited on the surfaces the molds during the production of the castings. The types and compositions of the borides and carboborides formed in the alloyed layer are determined. The effect of the parameters of the alloyed layer on the properties of the composite castings is analyzed.