Comparison of microstructure and oxidation behavior of NiCoCrAlYSi laser cladding coating before and after high-current pulsed electron beam modification

Highlights: • NiCoCrAlYSi laser cladding coating was irradiated via a HCPEB technique. • Original micro-pores and segregation were eliminated and the remelted surface became compact and uniform. • Dislocations and nano-crystalline structures were obtained after HCPEB irradiation. • Restructuring of surface contributed to a very stable, continuous, slow-growing, and uniform α-Al₂O₃ scale. • HCPEB technique is an effective way to improve the service life of MCrAlYX-type coatings. -- Abstract: In this study, NiCoCrAlYSi coatings prepared via laser cladding were modified using a high-current pulsed electron beam (HCPEB) technique. The microstructural modifications and the effects that the HCPEB treatment had on the high-temperature oxidation resistance were investigated. Microstructural observations reveal that the cladding coating surface, which was initially porous and composed of dendritic segregations, was totally changed after HCPEB irradiation; specifically, the microstructure became rather dense, and the composition became uniform. The grain refinement and high density of dislocations were obtained in the remelted layer. After oxidation for 100 h, the original coating showed relatively poor oxidation resistance, presented as severe internal oxidation. After HCPEB irradiation, the modified coating samples promoted the rapid formation of a stable, continuous, and slow-growing α-Al₂O₃ scale, which effectively prolonged the high-temperature life of the cladding coating.