Muhammad Rafi Raza

Role of Debinding to Control Mechanical Properties of Powder Injection Molded 316L Stainless Steel

316L stainless steel is widely used in various industries due to low cost, ease of availability and exceptional combination of mechanical properties along with corrosion resistance as compared to the other available metal alloys. In powder injection molding, debinding is very critical step and improper debinding can change the final properties dramatically. In the present study, affects of debinding on mechanical properties of powder injection molded 316L stainless steel were studied. The prepared feedstocks were molded according to MPIF 50 standard using vertical injection molding machine (KSA100). The plastic binder was removed at 450°C from the molded test samples using two different furnaces i.e. commercial and laboratory furnace followed by the sintering in vacuum, hydrogen, mixture of H2 and N2 (9:1) and nitrogen at 1325°C for 2hr with post sintering cooling rate 3°C/min . Test samples debound in commercially available furnace showed 97% densification and higher mechanical properties. The corrosion resistance was reduced due to presence of residual carbon during thermal debinding. The presence of carbon and formation of carbides and nitrides were confirmed by XRD and microstructural analysis. The results showed that the test samples debound in commercial furnace showed brittle behavior due to the presence of carbides and nitrides. Test samples sintered in N2 showed 96.3% density and tensile strength 751MPa. This value of strength is twice as compared to the sample debound in laboratory furnace followed by the sintering in vacuum. The achieved mechanical properties in vacuum sintered samples were comparable to the wrought 316L stainless steel (according to ASTM standard).

Effects of Residual Carbon on Microstructure and Surface Roughness of PIM 316L Stainless Steel

Powder injection molding (PIM) offers an attractive method for producing smart and intricate shapes components. PIM process is cost effective and equally applicable for metals and ceramics. Debinding process is the most critical step among all PIM steps and any residual during debinding can change the composition of sintered product resulting change in final properties. In this research work, the injection molded samples were thermally debound and sintered in various atmospheres. The results showed that the sintered samples with improper thermal debinding resulted the carbide formation at the surface and across the grain boundaries that caused to increase the roughness value.

Uniform Dispersion of Multiwalled Carbon Nanotubes in Copper Matrix Nanocomposites Using Metal Injection Molding Technique

This work presents a novel fabrication approach of multiwalled carbon nanotubes (MWNTs) reinforced copper (Cu) matrix nanocomposites. A combination of nanoscale dispersion of functionalized MWNTs in low viscose media of dissolved paraffin wax under sonication treatment followed by metal injection molding (MIM) technique was adopted. MWNTs contents were varied from 0 to 10 vol.%. Information about the degree of purification and functionalization processes, evidences on the existence of the functional groups, effect of sonication time on the treated MWNTs, and microstructural analysis of the fabricated Cu/MWNTs nanocomposites were determined using TEM, EDX, FESEM, and Raman spectroscopy analysis. The results showed that the impurities of the pristine MWNTs such as Fe, Ni catalyst, and the amorphous carbon have been significantly removed after purification process. Meanwhile, FESEM and TEM observations showed high stability of MWNTs at elevated temperatures and uniform dispersion of MWNTs in Cu matrix at different volume fractions and sintering temperatures (950, 1000 & 1050°C). The experimentally measured thermal conductivities of Cu/MWNTs nanocomposites showed remarkable increase (11.25% higher than sintered pure Cu) with addition of 1 vol.% MWNTs, and slight decrease below the value of sintered Cu at 5 and 10 vol.% MWNTs.