Characterisation of electrodeposited and heat-treated Ni−Mo−P coatings

Abstract

A eletrodeposição e as propriedades de dureza e resistência à corrosão de eletrodepósitos de Ni−Mo−P foram estudadas. A caracterização das camadas foi feita por microscopia eletrônica de varredura, difração de raios X e energia dispersiva de raios X. Os ensaios de corrosão foram feitos à temperatura ambiente em NaCl 10 -1 mol dm -3 e por polarização linear potenciodinâmica. Camadas amorfas de Ni−Mo−P foram obtidas e a composição destas mostrou ser dependente da composição do banho, da densidade de corrente aplicada e da temperatura do banho. A dureza das camadas de Ni−Mo−P mostrou ser dependente dos teores de Mo e P e que a ausência de trincas é um requerimento necessário para obter eletrodepósitos de Ni−Mo−P com boas propriedades de dureza. A dureza das camadas tratadas termicamente aumentou com a temperatura de tratamento térmico devido à precipitação das fases Ni, Ni 3 P e NiMo durante o tratamento térmico. A resistência à corrosão dos eletrodepósitos de Ni−Mo−P aumentou com o teor de P na camada. A camada Ni 78 Mo 10 P 12 apresentou os maiores valores de dureza a a maior resistência à corrosão. A adição de P mostrou ser benéfica para as propriedades de dureza e resistência à corrosão de eletrodepósitos de Ni−Mo.The electrodeposition, hardness and corrosion resistance properties of Ni−Mo−P coatings were investigated. Characterisations of the electrodeposited coatings were carried out using scanning electron microscopy, X-ray diffraction and energy dispersive X-ray analysis techniques. Corrosion tests were performed at room temperature in 10 -1 mol dm -3 NaCl solutions and by potentiodynamic linear polarisation. Amorphous Ni−Mo−P coatings were successfully obtained by electrodeposition using direct current. The coating composition showed to be dependent on the bath composition, current density and bath temperature. Both P and Mo contents contribute for the hardness properties of the Ni−Mo−P coatings and the absence of cracks is a requirement to produce electrodeposited Ni−Mo−P coatings with good hardness properties. The hardness values increase with heat-treatment temperature due to the precipitation of Ni, Ni 3 P and NiMo phases during the heat treatment. The corrosion resistance of the electrodeposited Ni−Mo−P amorphous coatings increases with P content in the layer. Among the electrodeposited Ni−Mo−P amorphous coatings, Ni 78 Mo 10 P 12 presented the best hardness and corrosion-resistance properties. The results showed that the addition of P is beneficial for the hardness and corrosion resistance properties of the Ni−Mo-based coatings.

Effect of Annealing Temperature on the Corrosion Resistance of Electroless Ni-B-Mo Coatings

“…In earlier studies, it is concluded that this change in structure causes an increase in hardness and wear resistance because of the formation of grains and hard precipitations (Ref [13][14][15]. Adding refractory metal molybdenum in the Ni-P coatings improved functional properties like thermal stability and preventing crystallization of amorphous structure by increasing crystallization transformation temperature (Ref [16][17][18][19][20]. Very limited investigation has been carried out on the effect of adding molybdenum (Mo) on the Ni-B coatings.…”

Microstructure and Properties of SUS304 Stainless Steel Joints Brazed with Electrodeposited Ni-Cr-P Alloy Coatings

“…This means that the electrodeposited Ni-13.4Cr-11.6P alloy coating has an amorphous structure. The formation of amorphous structure can be ascribed to the incorporation of phosphorus in the deposit [ 22 , 23 , 24 ]. In addition, the sharp peaks in the XRD diffraction pattern originated from the Cu substrate and the Al jig.…”

Influence of bath composition on the electrodeposition of amorphous Ni‐Mo alloys using potassium‐sodium tartrate as complexing agent

“…Other works for Mo electrodeposition performed at the same temperature condition are reported in the literature. [34,35] All deposits were obtained in quiescent conditions. Depositions were complete at an electric charge of 300 C.…”