Investigation of the effects of tungsten and boron carbide addition on the properties of electroless Ni-B coating

Properties of materials that matches with target properties provide an effective and safe usage. Surface of the materials is the part that faces with high forces and corrosive environments most of the time. In such cases, improving surface properties becomes a sensible application. Surface properties can be developed with many traditional and state of art methods. More recently, electroless coating methods by using aqueous solutions gained an importance because of their properties like low cost, ease of production, good corrosion properties, wear resistance etc. Electoless Ni coating is a populer method among obtaining metal deposits by auqueous solutions. In this work, electroless Ni-B coatings are produced with a new point of view since it has a wide usage in automotive and defense industries. Four different kinds of electroless coatings were produced (Ni-B, Ni-B-W, Ni-B-B4C and Ni-B-W-B4C) on AISI 4140 substrates by using four different coating baths. Addition of W and B4C on traditional Ni-B coatings were investigated by means of their effects, similarities, superiorities and weaknesses compared to each other. W addition improved nodule size of the coating, while B4C addition reduced it. B4C addition decreased coating thickness. Both W and B4C additions improved hardness of the coatings. The highest hardness and wear resistance is obtained for Ni-B-W-B4C, Ni-B-B4C, Ni-B-W and Ni-B coatings, respectively. However, highest corrosion resistance is achieved for Ni-B coating.