Reactive casting coatings for obtaining in situ composite layers based on Fe alloys

Abstract

Casting coatings were prepared on the basis of 2, 5, and 10% aqueous solutions of carboxymethylcellulose (CMC) (as a binder) with additions of powdered substrates of the forming reaction of titanium carbide (TiC). These substrates were in powder form; i.e., graphite (Cgr) and titanium (Ti). These coatings were investigated, and their viscosity, wettability, and gas volume emission were determined. Then, the coatings of the best rheological and physicochemical properties were singled out and used for fabricating the composite layers in the steel casting. The technological process was based on covering the casting mold cavity with coatings containing substrates of the TiC formation. The temperature of the casting alloy was the factor initiating the synthesis reaction of the TiC. The produced in situ composite layers were characterized by estimating their thickness, structure, microstructure, chemical composition, and hardness. To this aim, the X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), and the Vickers-type hardness tester were used. The obtained layers were 1 mm to 1.2 mm thick, while their structures were not homogenous due to the reactive infiltration effect causing their fragmentation. The presence of the ceramic phase in the TiC form was found within the layer zone; as a result, a hardness of 600 HV1 to 750 HV1 was achieved. The average hardness depended on the chemical composition of the applied coatings.