Spark plasma sintering of nickel and nickel based alloys: A Review

Abstract The use of spark plasma sintering technique has been identified as a means of enhancing materials properties, especially nickel-based alloys. Nickel and nickel-based alloys are essential materials that combine different properties which include; high-temperature strength, good mechanical properties, appreciable toughness, resistance to thermal shock, resistance to thermal fatigue, resistance to chemical attack, resistance to creep, resistance to corrosion/oxidation and good surface stability at the high-temperature environment. The above qualities have made alloys gain more patronage and acceptance in recent time. However, a higher percentage of the demand comes from the aerospace industry, gas/steam power plant, petrochemical plant, nuclear reactors and marine industry. Spark plasma sintering is one of the powder processing methods in metallurgy that has been used to fabricate nickel-based alloys with exceptional qualities. The process involves, mixing metallic powders to form the desired stoichiometry composition (in the case of forming an alloy), either by direct mixing or mechanical alloying. The already mixed powder is transfer to a graphite mould and then compacted in the heating chamber of the furnace. Heat is supply to sinter the compacted powder at a temperature below the alloy melting point, in order to ensure metallurgical bonding between the powder particles. The application of spark plasma sintering technology is a promising one, especially for processing nickel alloys. It promotes the formation of gamma (γ) matrix phase, gamma prime (γ’) intermetallic phases, secondary gamma prime (γ”) intermetallic phase and precipitation of solid solution strengthening elements. These are the phases that improve the mechanical properties of sintered alloys. Spark plasma sintering minimizes the problems associated with conventional fabricating routes such as; micro segregation, pores and pin holes.