Formation of hard tungsten boride layer by spark plasma sintering boriding

Abstract

Metal borides are attractive candidates for high-temperature, wear resistance, and corrosion resistance applications. Tungsten borides (WB and W₂B₅) are known to have high hardness values, chemical inertness, and electronic conductivity, and have potential industrial applications as abrasive, corrosion-resistant and electrode materials, which are exposed to exacting environments. In this work, boride layers are formed on the surface of W samples using a pack boriding method with the assistant of the spark plasma sintering technique. The process was performed in the temperature range 1000-1400 °C with a holding time of 30 min. The microstructure, microhardness, and fracture toughness of the tungsten boride layer are investigated by optical microscopy, X-ray diffraction and microhardness indentations. Results showed that the boride layer, composed of WB, have thickness in the range ~35-112 μm. The WB layers are found to have a preferred orientation in the (200) direction, which is reflected by a distinct columnar growth observed in the optical micrographs of polished cross-sections of SPS samples.