Nickel-boron coatings

Hydrazine—borane compounds are made by the reaction of sodium borohydride and a hydrazine salt in THF (23,24). The mono-(N2H4 BH ) and di-(N2H4 2BH2) adducts are obtained, depending on the reaction conditions. These compounds have been suggested as rocket fuels (25) and for chemical deposition of nickel—boron alloys on nonmetallic surfaces (see Metallic COATINGS) (26). 

In recent years, the spraying process has been adapted for hard facing, using the chromium-nickel-boron alloys which have become known as Colmonoy. More recently still, the cobalt-base Stellite alloys have also been used. These materials in powder form are sprayed on to the surface in the usual way. The deposit is afterwards heat treated by a torch, so that fusion takes place. The process is often known as spray-welding. Such coatings are primarily used for hard facing under wear conditions, but as the Anal surface is nickel-chromium or cobalt-chromium they exhibit very high anticorrosive properties. 

Electroless nickel-phosphorus should not be used with either fused or hot, strong, aqueous caustic solutions because the coating offers lower resistance to attack than does electrodeposited nickel. As-deposited electroless nickel-boron, however, offers good resistance to hot aqueous caustic solutions It is also resistant to solutions of oxidising salts such as potassium dichromate, permanganate, chlorate and nitrate. 

Zvyagintseva A.V., Falytcheva A.Y. (1997) Physico-mechanical properties of nickel-boron coatings, Galvanotechnique and surface treatment 2 (5), 24-31. 

Our work aims to developed a scientific and engineering background in the production of Nickel boron alloys (NiB) which can be used as a brazing material, wear-corrosion-oxidation resistive applications via carbothermic reduction that is the effective and attractive process technique regarding high mass of production for industry such as brazing, automotive, electronics, aircrafts, coatings etc. 

Electroless Ni coatings are produced by autocatalyt-ical reduction of Ni ions from aqueous solution. Three electroless coatings are applied most frequently nickel-phosphorus (6-12wt%P), nickel-boron ( 5wt%B), and composite coatings (Ni—P with SiC, fluorocarbons, and diamond). A more extensive account is given in [1.96]. 

Surfaces can also be coated without involving electricity. Electroless nickel plating, for example, involves pretreating the surface of any material, including nonconductive materials, with a catalyst such as sodium hypophosphite. This treated surface is then immersed in a heated nickel-phosphorous or nickel-boron solution. The metal ions from the solution are reduced to metal in contact with the catalyst and form a dense alloy layer on the treated surface. 

Nickel-boron coatings have excellent resistance to wear and abrasion, but because they are not completely amorphous they have reduced resistance to corrosive envirorunents. Furthermore, they are much more costly than nickel-phosphorus coatings. 

Fluorinated surfactants improve the quality of electroless plating of copper [67,68] and stabilize the coating bath to deposit nickel-boron layers without a dentritic layer structure [69]. 

Furman, V.V., Gaiduchenko, G.K., Vlastuk, R.Z. and Oeimontovich, V.B., Structure and properties of electrophoretic chromium carbide coatings with a eutectic composition nickel-boron binder, Sov. Powder Metall. S Met. Ceram. 22 942-45 (1983). 

Another important function of metallic coatings is to provide wear resistance. Hard chromium, electroless nickel, composites of nickel and diamond, or diffusion or vapor-phase deposits of sUicon carbide [409-21-2], SiC , SiC tungsten carbide [56780-56-4], WC and boron carbide [12069-32-8], B4C, are examples. Chemical resistance at high temperatures is provided by aUoys of aluminum and platinum [7440-06-4] or other precious metals (10—14). 

Electroless Electrolytic Plating. In electroless or autocatalytic plating, no external voltage/current source is required (21). The voltage/current is suppHed by the chemical reduction of an agent at the deposit surface. The reduction reaction must be catalyzed, and often boron or phosphoms is used as the catalyst. Materials that are commonly deposited by electroless plating (qv) are Ni, Cu, Au, Pd, Pt, Ag, Co, and Ni—Fe (permalloy). In order to initiate the electroless deposition process, a catalyst must be present on the surface. A common catalyst for electroless nickel is tin. Often an accelerator is needed to remove the protective coat on the catalysis and start the reaction. 

Properties of the deposits Almost any material which can be melted is suitable for plasma spraying, giving a vast range of possible coatings of single or mixed metallic or non-metallic substances. It is often possible to produce types of coatings which are not obtainable in any other way. Typical of the materials which are plasma sprayed are copper, nickel, tantalum, molybdenum. Stellites, alumina, zirconia, tungsten and boron carbides, and stainless steels. 

Nicotine adenine dinucleotide phosphate (NADP+), 24 147 Nicotinic acid, 9 477-478 26 291 alkaloid precursor, 2 78 Ni-Cr alloys, 23 499. See also Nickel-chromium entries NiCrAlY coatings, 13 508 nido designation boranes, 4 184-186 boron hydrides, 4 170, 172-176 Nidrel, molecular formula and structure, 5 129t... 

Hack Diffusion. Pack diffusion or cementation processes are similar 10 pack carburizing, anil are used to coat iron, nickel, cuhali. and coppci with chromium, boron, zinc (Sheradi/ingl. aluminum, silicon, titanium, molybdenum, and other metals. 

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