Effect of Tungsten Carbide Morphology, Quantity, and Microstructure on Wear of a Hardfacing Layer Manufactured by Plasma Transferred Arc Welding

Hardfacing layers on mild steel substrates were successfully manufactured using a plasma transferred arc welding (PTAW) process to combine tungsten carbide powder and binder metal. Three morphological types of tungsten carbide powder were employed: spherical, fused angular, and mixed powder. The effects of both the morphology and the quantity of tungsten carbide powder on the wear property of the products were determined using a dry sand wheel abrasion test. The results revealed that two conditions effectively increased the wear resistance of the hardfacing layers: the use of spherical tungsten carbide and the use of an increased quantity of tungsten carbide. Moreover, the formation of an interfacial layer of intermetallic compounds (IMCs) between the tungsten carbide and binder metal, and the relationship between the microstructure of the IMC layer and its wear property were also investigated. It was confirmed that, in general, preferential wear occurs in the binder metal region. It was also unveiled that the wear property improves when interfacial IMC bands are formed and grown to appropriate width. To obtain a sound layer more resistant to wear, the PTAW conditions should be adequately controlled. In particular, these include the process peak temperature and the cooling rate, which affect the formation of the microstructure.

STRENGTHENING OF CARBIDE STEEL SURFACE BY TUNGSTEN CARBIDE POWDER BY PLASTIC DEFORMATION

The use of the technology of combined electromechanical processing, consisting of a high-temperature plastic deformation mode, when tungsten carbide powder is implanted into the surface of carbon steel, and a high-temperature thermal hardening mode, during which tungsten carbides are partially dissolved in the austenite of steel up to the limit of its saturation with tungsten, provided a gradient wear-resistant three-layer highly dispersed structure as a result of the decomposition of supercooled austenite oversaturated with tungsten. The results of tribotechnical tests of cylindrical specimens by the normalized method are presented.

Studying the microhardness on the surface of SKD61 in PMEDM using tungsten carbide powder

Electrical discharge machining (EDM) process is widely used to process hard materials in the industry. The process of electrical discharge is changed and called PMEDM when alloy powder is added in the oil dielectric. In this study, the effect of tungsten carbide alloy powder added in the dielectric on the microhardness of surface (HV) status of the workpiece SKD61 after machining is investigated. Studies show that the microhardness of surface obtained by PMEDM is generally better than that by normal EDM. The experiment shows that at the selected process window, adding the powder has resulted in an improvement of the microhardness up to 129.17%.

RECENT DEVELOPMENT OF FRICTION STIR WELDING TOOLS FOR JOINING COPPER ALLOYS

In the present work an attempt was made to develop low cost high temperature wear resistance hardfacing tools. The hardfacing was applied on mild steel rod using Tungsten carbide powder by Plasma transferred arc welding (PTAW) processes. A comparative study was done to study the performance of hard facing tools with conventional tools. In this work, friction stir welding of pure copper plate of 6 mm thickness was investigated with an aim to understand the performance of tool materials on weld microstructure and tensile properties. From this investigation, it is found that the joints fabricated using PTA hardfaced tool yielded superior tensile properties compared to other joints. The optimum level of heat generation, formation of fine grains and higher hardness in plasticized zone are the main reasons for the superior tensile properties of these joints.