Stainless steel matrix composites reinforced with AlCr2

The effect of AlCr2 intermetallic addition to austenitic stainless steel powder on the mechanical properties and corrosion resistance of sintered specimens has been investigated. It has been recognised that loss of chromium at the grain boundaries of sintered stainless steel decreases its corrosion resistance. With the objective of decreasing this effect and to keep a stable passivity, the intermetallic AlCr2 in the form of powder was mixed with AISI 316L in different proportions. Samples of these materials were compacted at 700 MPa and sintered at 1120 degrees C for 30 minutes in dissociated ammonia and vacuum. The mechanical properties, the corrosion resistance and the microstructure were studied. Composite materials sintered in dissociated ammonia achieve higher mechanical properties than sintered in vacuum. Studies realised by SEM suggest that metal matrix composites present an increase in the content of chromium, but in the grain boundaries exhibit a transient liquid phase produced by diffusion of aluminium from AlCr2.