Abstract
This work assessed Ni-based C276 alloy coatings by PTA with different degree of interaction with AISI 316L and API 5L X70 steel substrates. Track geometry, dilution and microstructure of coatings were evaluated by optical, scanning electron microscopy and X-ray diffraction. Properties were evaluated by hardness and wear tests. Microstructure exhibited austenite Ni-FCC dendrites and interdendrictic regions containing carbides. Dilution from 4,9 to 25,4% for coatings on API 5L X70 leaded to hardness ranging from 283 to 243 HV0,5. Otherwise, dilution between 22,3 and 41,5% for coatings on AISI 316L induced hardness from 267 to 225 HV0,5. Higher interaction with the substrate leaded to 19,8% increase of mass loss rate on API 5L X70 coatings. The slight difference for coatings properties deposited on different substrates indicated that the degree of interaction was the most significant factor.
Highlights
Coatings have been applied to protect components surface in different applications[1]
Nickel-based alloy was deposited by PTA with a starweld PTA 300M equipment using the commercial atomized alloy of Stellite kown as Hastelloy C276, with grain size ranging from 90 to 150μm on AISI 316L stainless steel 12,5mm thick and API 5L X70 steel 10,0mm thick plates
The lowest wettability was measured processing NiCrMo C276 alloy with 120 A, confirmed by the highest wettability angle (Θ), reinforcement thickness (t) and shallowest width compared to coatings processed with higher current (150 and 180A), Table 3
Summary
Coatings have been applied to protect components surface in different applications[1]. Nickel-based alloys are used to extend campaign of engineering components in many industrial areas including chemical processing, nuclear power plants, marine engineering and oil and gas industry, mainly involving corrosion and/or heat resistance[2,3,4,5]. Besides the effect of solid solution and second phase (carbide) on strengthening, Chromium contents higher than 15% improve oxidation and carburization resistance because of the formation of a protective oxide layer on the surface. The Nickel base of the alloy allows the retention of this formed superficial protective layer, especially on cyclic exposures at high temperature[3,6,7,8,9,10]. This work evaluated the effect of substrate on characteristics of Nickel-based coatings by plasma transferred arc thru processing current intensity variation in order to achieve different interaction degrees (dilution) with the substrate. The impact of coatings microstructure on properties was assessed by hardness and abrasive sliding wear tests
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