Investigation of bonding strength and hot corrosion behavior of NiCoCrAlSi high entropy alloy applied on IN-738 superalloy by SPS method

Abstract

Fabrication feasibility of NiCoCrAlSi/IN-738 (HEA-15), NiCoCrAlSi/Al/IN-738 (HEA-15F) joints via plasma spark sintering (SPS) method was investigated in this study. The bonding strength and hot corrosion behavior of these systems are compared with NiCrAlY/IN-738 (NiCrAlY) joint. The mentioned high entropy alloys (HEAs) were fabricated by mechanical alloying method for 40 h in Ar atmosphere. The milled powders were then applied on IN-738 superalloy by SPS method at 1170 °C and soaking time of 15 min with an average thickness of 1.1 mm. The microstructural/phase characterization of these samples was evaluated by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The hot corrosion behavior of these joints in 90 wt% Na 2 SO 4 − 10% wt. NaCl at 800 °C for 100 h were studied. Bonding strengths were evaluated using the pull-off adhesion test. The lowest amount of hot corrosion was obtained for the HEA-15 joint. The highest thickness of oxide layers after the hot corrosion test was obtained for the NiCrAlY sample (366 µm), which was higher than the HEA-15 sample (194 µm). High bonding strength of 155 MPa was obtained for HEA-15 sample which was higher than that of the other joints. This value was 114 MPa for NiCrAlY joint. Contrary to expectations, HEA-15 F sample did not show appropriate bonding strength due to the presence of surface oxides in aluminum intermediate layer. • NiCoCrAlSi high entropy alloy and NiCrAlY are applied on IN-738 by SPS method with an average thickness of 1.1 mm. • Bonding strength and hot corrosion behavior of these systems were compared. • The lowest amount of hot corrosion was obtained for the HEA-15 joint. • The highest thickness of oxide layers after the hot corrosion test was obtained for the NiCrAlY sample. • HEA-15 joint showed more bonding strength than that of the other samples.