Abstract
Electron beam (EB) technology treatment was carried out on CoNiCrAlY bond coats deposited on Inconel substrates via cold spray and HVOF techniques in dissimilar thicknesses. Such treatment was carried out with regard to the final materials microstructure, composition, surface roughness, and the quality of the coating-substrate interface. Following a multiple-step optimization of the processing parameters (such as beam pattern configuration, accelerating voltage, longitudinal speed, and multiple beam incidence), two final EB modifications were carried out on both coating types. It was found that the optimized EB treatment could lead to a significant alteration of the interface from a distinctive divide into smooth chemical and structural transition between the materials, significant decrease in surface roughness and porosity, and changes in mechanical properties (increase in Young’s modulus and decrease in hardness of the coating).
Highlights
New-generation electron beam treatment [1] of materials has been successfully used in various applications such as deep welding [2, 3], melting [4,5,6], cladding and precipitation [7], heat-treatment and recrystallization, synthesis [8], structure and properties modification [9,10,11], or, for example, hardening [12, 13]
Resistant to elevated temperatures, MCrAlY coatings are commonly used as bond coats for ceramic-based thermal barrier coatings (TBC, often ZrO2 + Y2O3) topcoats
A good quality transient interface was obtained for coatings deposited via cold spray and HVOF technologies at dissimilar thicknesses
Summary
New-generation electron beam treatment [1] of materials has been successfully used in various applications such as deep welding [2, 3], (selective) melting [4,5,6], cladding and precipitation [7], heat-treatment and recrystallization, synthesis [8], structure and properties modification [9,10,11], or, for example, hardening [12, 13]. The modification of structure related to joining of dissimilar materials (often via welding) is primarily based on rapid thermal input and (selective) melting of one or both of the components. Such processing involves materials in liquid phase which might affect the resulting microstructure. Resistant to elevated temperatures, MCrAlY (frequently, M = Co, Ni, or both) coatings are commonly used as bond coats for ceramic-based thermal barrier coatings (TBC, often ZrO2 + Y2O3) topcoats Their composition is similar to that of superalloys used at high temperatures but is generally richer in Al and Cr to promote a formation of a protective oxide scale. These may lead to changes in the mechanical properties and a potential failure [15,16,17]
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