Instytut Podstawowych Problemów Techniki

UMO-2017/25/B/ST8/01789

2018-03-05 / 2022-03-04

Jedyny wykonawca

NCN

OPUS

13

During latest years the transition metal borides due to their combination of outstanding physical properties such as metallic conductivity, high incompressibility, high shear strength, and exceptionally high hardness have attracted attention amongst materials researchers. All of these attributes are desirable in materials for structural and engineering compounds and could positively indicated that borides may be suitable replacements for current metal carbides in next-generation cutting tools. This project represents a significant step forward the search for low-cost, easily manufactured hard materials. When ReB2 was first shown to be super-hard at low loads(Hv= 40.5 GPa), the results were heralded as a breakthrough in hard materials. At the same time, it was clear that ReB2 would be less likely to result in a practical system because of the high cost of Re and fast corrosion. WBx are a comparatively low-cost materials, and the data from recent investigations show that it can be converted to a material with significantly higher hardness than ReB2 by the addition of small amounts of relatively low-cost elements. Also the increasing industrial demand for protective coatings with high hardness, good elastic properties and thermal stability calls for the investigation of new material systems. This project concerns study of deposition of thin films of new super-hard materials as ternary tungsten borides WxTMx-1By where TM = Re, Ti, Zr, Mo, Cr. Coatings will be deposited by Pulsed Laser Deposition (PLD), magnetron sputtering and combination of both of this method. The targets will be made by SPS methods. We propose also numerical prediction of structural, mechanical and optical properties of these superhard metallic ternary borides. The examination of targets and deposited films together with experimental monitoring and theoretical investigation of processes occurring during deposition should lead to determination of conditions necessary for formation of reliable, super-hard coatings – the ultimate goal of the project. Also the attempt to developing of new deposition method – combined PLD with magnetron sputtering will be taken. The aim of this project is to produce and studding of properties of tungsten borides coatings such as WB, WB2 and WB3 doped by Re, Ti, Zr, Mo, Cr . Those are the most interesting structures of ternary borides, because their hardness should significantly increase in comparison with WBx. For example hardness of W0.92Zr0.08B4 is 55.9 ± 2.7 GPa when WB4 is only 40 GPa. The coatings will be deposited by magnetron sputtering method or PLD using sputtering targets of doped tungsten borides having a different molar ratio of Re, Ti, Zr, Mo, Cr to tungsten. Also combination of two magnetrons or laser and magnetron is planned where the first target will be made from tungsten borides and second from dopant. Magnetron sputtering enables effective control over the structure of material at the level of atoms and molecules. By the modification of the parameters of deposition, such as the sputtering power, the pressure and the type of working gas, and the temperature of the substrate, the control of the microstructure and obtain nano-grain material will be possible. Moreover, the magnetron sputtering allows the high production repeatability. On the other hand the PLD method is versatile and suits very well for deposition of hardly meltable metals as Re and W. The beam intensity of a conventional Nd:YAG laser at the focal spot on the target is easily in the range of GW/cm2, which means that the laser can evaporate any known material. The main advantage of PLD is composition preserving. It should be underlined that this will be a first systematic study of various compounds of ternary tungsten borides in the form of thin films, connecting the deposition parameters, internal structure of the material, and its functional properties. The modern research techniques will be used to investigation of properties of deposited coatings. The surface roughness will be measured by an atomic force microscope (locally) and microscopic optical profilometer (globally). The internal structure of materials and determination of the type of formed chemical compound will be studied by X-ray diffraction and transmission electron microscopy. For well characterized coatings will be examined the mechanical and chemical properties such as hardness, fracture toughness and thermal stability. The hardness and fracture toughness will be tested in a nanoindentation test. The thermal stability of the coatings will be studied in depth on the basis of changes in the structure of the material after annealing at temperatures of from 300 to 1000 ° C. For structural calculations DFT method will be used.