Structure, Mechanical Properties and Wear Resistance of High-vanadium Cast Iron

Abstract

A series of melts with carbon content 1.38–4.16% and that of vanadium 5.25–15.50% was made. The X-ray diffraction of the examined alloys revealed the presence of three phases, i.e. ferrite, alloyed cementite, and VC_x carbide. The relationships between the content of carbon and vanadium corresponding to eutectic structure (the eutectic line) as well as the degree of eutectic saturation S_c were determined. Besides eutectics, the high-vanadium cast iron holds the following constituents in its matrix: alloyed ferrite, granular pearlite, and lamellar pearlite as well as a mixture of alloyed ferrite+granular pearlite, granular pearlite+lamellar pearlite. The results show that passing from ferritic matrix through granular pearlitic and to lamellar pearlitic matrix, hardness HB, tensile strength R_m, and yield strength R_0.2, increases while plastic properties of alloys represented by elongation A₅ decreases. The wear behaviour of alloys was tested in two different modes “specimen-abrasive paper” test (P1) and “specimen-counterspecimen” test (P2). The results obtained in test P1 are following: a) alloys with ferritic matrix and of the lowest hardness (182–189 HB) are characterised by the lowest abrasion wear resistance (s=3.14–3.93 mg/m), b) in alloys with a pearlitic matrix and hardness in the range of 387–416 HB the abrasion wear resistance is comparable to that of Hadfield cast steel (about s=2 mg/m) and c) cast iron with lamellar pearlite+granular pearlite matrix and hardness 322 to 401 HB gives the highest abrasion wear resistance of s=0.24–0.62 mg/m. In general, it can be stated that the abrasion wear in test P2 is higher than in test P1.