TESTING OF REGENERATIVE THERMAL SPRAYING Ni-Al ALLOY COATINGS

The article presents the results of testing of Ni-Al alloy coatings with different chemical constitution and phase composition, which might replace currently used electrolytic chromium coatings.Crust chromium coatings are suitable for reconditioning of machine parts because of their very good maintenance properties. However, due to toxicity of electrolylic chromium bath, their application tends to be restricted. Thermal flame and plasma spraying technologies were chosen for nickel aluminium coating application. Obtained coatings were distinguished by significant porosity of structure and surface roughness. The thickness of coatings ranged from 440 to 683 µm. Microhardness of coatings was not related to applied metal plating technology but to chemical constitution and phase composition. The more aluminium content in alloy coating the harder the coatings were. The hardness of coatings which resulted from NiAl phase was ca 250 HV 0.04. Flame spray coatings are distinguished by nearly 10 times bigger corrosion current density when compared with plasma spray coatings.The value of corrosion potential is influenced by structure and chemical constitution of coatings. The more aluminium content the lower Ecorr. Key words: thermal spraying, regenerative coatings, nickel-aluminium coatings 1