Effect of homogenizing treatment on microstructure and microhardness of GH3536 and GH4169 alloy by selective laser melting

Abstract

GH3536 and GH4169 nickel-based superalloys are widely used in aerospace engines and other hot-end components. In this paper，GH3536 and GH4169 alloy samples were fabricated by optimizing the process parameters using selective laser melting（SLM），the defect characteristics and microstructure of two alloys，as well as the effects of different homogenization temperatures and holding times on microstructure evolution，average grain size，and properties of two alloys were studied. The defect characteristics and microstructure were investigated by OM，SEM，and EDS, et al. The Vickers hardness meter was used to test the alloy’s microhardness. The results indicate that the as-built GH3536 alloy exhibits more defects，including pores，cracks，and lack of fusion， while only pores are present in as-built GH4169 alloy. The melt pool of alloy is eliminated by homogenization treatment，and the grains grow into equiaxed grains. M23C6 are found to distribute within grain boundaries and grain interiors of GH3536 alloy，while NbC are found to distribute within grain boundaries and grain interiors of GH4169 alloy，and the amount of precipitates is significantly reduced with the increase of homogenization temperature. The average grain size of GH3536 alloy is increased by 106.8% from 48.5 μm at 1130 ℃/1 h to 100.9 μm at 1250 ℃/4 h . The grain size of GH4169 alloy is increased by 53.3% from 57 μm at 1080 ℃/1 h to 87.4 μm at 1200 ℃/4 h.The homogenization treatment of GH3536 alloy and GH4169 alloy results in a significant decrease in microhardness of the former，from 262HV to 180-190HV，while the latter shows a significant increase，from 313HV to 430-450HV.

Keywords

• selective laser melting
• gh3536
• gh4169
• microstructure
• homogenizing treatment
• average grain size
• microhardness