Formation and Structural Characterization of Electroless Ni-B-P Ternary Alloy Coatings

Abstract

The aim of the present investigation is to study the formation of electroless Ni-B-P alloy coatings and structural and morphological characterization of various coatings with different boron and phosphorous content. An alkaline plating bath with nickel chloride hexahydrate as the source of nickel ions and sodium borohydride and sodium hypophosphite as reducing agents were used for the formation of electroless Ni-B-P alloy coatings. The influence of changes in the concentrations of the reducing agents in the electroless plating bath on the chemical composition, structural and morphological characteristics of the coatings were studied. Scanning electron microscopic studies revealed that the surface morphology of Ni-B-P alloy coatings changed from corn cob-like structure to cauliflower-like structure with increasing borohydride concentration in electroless plating bath, whereas increase in hypophosphite concentration favoured sideway growth, thereby decreased the surface roughness of the Ni-B-P alloy coatings. The peak broadening in the X-Ray Diffraction profiles indicates the large reduction in the crystallite size of the electroless Ni-B-P alloy coatings with increasing boron content in the coating (i.e. for higher borohydride concentration in the plating bath).

Investigation of mechanical and tribological properties of electroless Ni-P-B ternary coatings on steel

“…Ni-P-B ternary depositions were executed earlier with various combinations. However, sodium borohydride and sodium hypophosphite combination came out to be an appropriate combination as reducing agents [7][8][9][10][11]. Venkatakrishnan et al [7] experimented with Ni-P-B combination on steel substrates with pH and temperature of the bath solution were maintained at 14 and 95 °C respectively.…”

“…Variation in concentration of both reducing agents has revealed more important information likewise the interlink mechanism between the two reducing agents. It has been found that concentration increment of sodium hypophosphite can directly affect the boron content because it was decreased with the increase of hypophosphite content, though hypophosphite concentration increment was proved to be very beneficial as surface roughness reduced [8]. Microhardness was also tested for both types of coated samples.…”

Mechanical properties of heat-treated duplex electroless nickel coatings

“…It is also well known that heat treatment in suitable conditions of electroless nickel coatings improves their mechanical properties [2,17,23-27] due to the formation of nickel phosphide or nickel–boride phases that are much harder than nickel [2,4,6,28-34]. This paper aims thus to investigate if the beneficial effects of heat treatment are similar for duplex coatings to those observed usually for ENP and ENB.…”

Elektrolitik Sert Metal Kaplamaya Alternatif Çevreye Duyarlı Ni-P Kaplamaların 6061 Serisi Alüminyum Altlık Üzerine Akımsız Yöntemle Biriktirilmesinde Sodyum hipofosfit, Sıcaklık ve Zamanın Etkisi

“…Kendi içlerinde düşük (%1-3), orta (%4-10) ve yüksek (%11-13) fosforlu kaplamalar olarak sınıflandırılabilir ve kaplama özellikleri yapıdaki fosfor miktarı ile doğrudan bağlantılıdır [4]. Akımsız Ni-P kaplama tekniği yüksek aşınma direnci, iyi yağlanabilirlik ve yüksek sertlik gibi özelliklere sahip olduğu için birçok alanda kullanılır [5][6][7][8][9]. Düşük fosfor içerikli (1-3 % P) kaplama kristalin olup iyi bir aşınma direnci fakat klorürlü ortamda düşük korozyon direnci sağlar.…”