Improving stability of thermal barrier coatings on magnesium alloy with electroless plated Ni–P interlayer

Deposition of duplex MAO layer/nanostructured titanium dioxide composite coatings on Mg–1%Ca alloy using a combined technique of air plasma spraying and micro arc oxidation

“…Plasma sprayed ceramic coatings were also used to greatly improve the corrosion, oxidation and wear resistances of the magnesium alloys [23e31]. However, the adhesion between the ceramic coating and the Mg substrate was considerably reduced due to the formation of a thermally grown oxide layer on the magnesium alloy during spraying [32]. In fact, plasma flame can directly affect Mg alloy surface and can easily oxidize Mg alloy surface (especially during plasma spraying materials with high melting point, such as ceramic materials).…”

“…This phenomenon can considerably reduce the attachment between sprayed ceramic layer and the Mg alloy. This case was observed by the spallation of the sprayed ceramic coating form the Mg substrate [24,26,28,31,32]. Therefore, the use of a metallic bond coat along with a reduction of the Mg alloy surface temperature has been suggested for this type of material during plasma spraying (especially when spraying ceramic materials on a Mg surface).…”

Microstructural characterisation of air plasma sprayed nanostructure ceramic coatings on Mg–1%Ca alloys (bonded by NiCoCrAlYTa alloy)

“…It is worth mentioning that the substrate temperature (because of the highly active nature of the Mg alloy) can considerably influence the performance and spallation of the plasma-sprayed coatings on the Mg alloy substrate during plasma spraying. When the plasma flame impacts the Mg alloy surface with high substrate temperatures, an Mg alloy layer comprising a thermally grown oxide (TGO) layer and creep deformation can be formed at the bond coat/Mg alloy interface [13,24,26]. This layer is also called the heat-affected layer (HAL).…”

“…However, the adhesion between the sprayed coating and the Mg substrate was considerably reduced owing to the formation of a thermally grown oxide layer on the magnesium alloy during spraying [24]. In fact, plasma flame can directly affect and easily oxidise a Mg alloy surface (especially during plasma spraying of materials with a high melting point such as ceramic materials).…”

“…These materials are able to provide excellent corrosion resistance for metallic substrates such as stainless steel, cobalt-chromium alloys and mild steel [22][23][24][25][26][27][28][29]. In particular, plasma sprayed nanostructure ceramic coatings derived from agglomerated feed stocks had much higher abrasive wear, thermal shock and corrosion resistance than the corresponding conventional coatings.…”