TO DEVELOP NEW ALLOY SYSTEMS BASED ON IRON-PHOSPHORUS AND EVALUATE THEIR MECHANICAL PROPERTIES

Abstract

High density Fe-P binary, Fe-P-Cr , Fe-P-C ternary as well as Fe-P based Fe-P-Si-Ni-Mo-Cu , Fe-P-Si-Ni-Mo-Cu-C and Fe-P-Si-Ni-Mo-Cu-.0-AI alloys were made using hot powder forging technique. In this process mild steel encapsulated hot powders (blend of Fe powder and ferro- phosphorus powder with ferro- silicon powder, ferro- molybdenum powder, copper powder, nickel powder and Aluminum powder, with/without carbon) were forged into slabs. Mild steel encapsulation was removed after homogenization of these slabs. The slabs were hot rolled to get highly densified sheets and wires. These highly densified products were annealed to relieve the residual stresses. Use of fine powder and high temperature processing in presence of H2 atmosphere facilitate densification. These alloys were characterized in terms of microstructure, porosity content / densification, hardness and tensile properties. Densification as high as 98.9% has been realize by adopting hot powder forging technique. Microstructure of these alloys consist of single phase ferrite only.Fe-0.35P-0.15C showed very high elongation (39%) in annealing state. Fe-0.35P-lSi-2Ni-0.5Mo-2Cu and Fe-0.35P-lSi-2Ni-0.5Mo-2Cu-.15C alloys showed higher strength (as high as 650 MPa) and higher hardness(as high as 330 Hv/10kgf). Fe-0.45P-lSi-2Ni-0.5Mo-2Cu alloy showed truly high strength (as high as 850 MPa) with higher hardness (360 Hv/10kgf) Fe-0.45P-1 Si-2Ni-0.5Mo-2Cu-0.15C alloy showed combination of very high strength with fairly higher -hardness (1015 Mpa, 398Hv/10kgf) due to combined •effect. of higher Phosphorus (0.45wt%) and small amount of Carbon (0.15wt%). Fe-0.40P-lSi-l.5Ni-0.5Mo-1.5Cu-0.3A1-0.25C alloy showed higher elongation (21%) with moderate strength and hardness (414MPa, 368hv/10kgf).This is something new. It was found that as Phosphorus content increased (0.35wt% to 0.45wt%) strength and hardness increased by expense of total elongation. Addition of Chromium in Fe-P binary alloys improved proof strength and ultimate tensile strength of alloys and also provide more easiness in forming operations as compare to Fe-P binary alloys. It is found in this present investigation that the alloying addition such as Mo, Ni, Si and C to Fe-P based alloys caused increased in strength associated with the reduction in ductility. The all alloys were capable of hot working to very thin gauge of sheet and wire.