Effect of Feedstock Powders on Microstructure and Properties of CoNiCrAlY Coatings
Two type powders of CoNiCrAlY alloy were prepared by gas atomization(GA)and water atomization(WA)respectively,then which were used as feedstock powders to further prepared the corre-sponding coatings on a directionally solidified high temperature alloy DZ411by using high velocity oxygen fuel(HVOF)technique and subsequently they were subjected to proper subsequent vacuum heat treat-ment.The flowability and apparent density of the prepared powders were measured according to GB/T 1484 and GB/T 1479.Meanwhile,the phase composition,microstructure,microhardness,and adhesive strength to the substrate of the prepared coatings were characterized via optical microscopy and scan-ning electron microscopy,automatic hardness tester,and universal testing machine.The high tempera-ture oxidation performance of the coatings/DZ411 was assessed in air at 1050℃ for 200 h.The results show that compared with WA,the CoNiCrAlY powder prepared by GA is spherical or nearly spherical,with good flowability and high apparent density.The prepared GA coating has a dense and uniform struc-ture with high β phase content,low porosity,high adhesive strength and high microhardness.After vacu-um heat treatment,mutual fusion of particles was clearly observed within the two coatings,while the amount of βphase increases and its distribution becomes much more uniform,correspondingly,their po-rosity and microhardness decrease.The adhesive strength of WA coating after vacuum heat treatment has been improved,but there are still larger pores within the coating.The vacuum heat treated GA coat-ing presents much better oxidation resistance.
surface and interface in the materialsgas atomizationwater atomizationCoNiCrAlY powderHVOF coatingvacuum heat treatmentmicrostructureproperties
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