Development of Three-Dimensional Non-Contact Surface Profilometer and Application to Evaluation of Impact Erosion of Metal Matrix Composites
A three dimensional non-contact surface profilometer system which can measure a wide area (order of square milli-meters) with high resolution (sub micro meter) has been completed. This system can measure the surface topography in the atmosphere by means of a confocal wavelength displacement sensor. We examined the optimum measurement conditions and applied them to the evaluation of erosion properties of particle reinforced metal composites. As a result, a scanning speed of 1mm/s and sampling intervals of 0.5-15μm were found to the optimum conditions. In addition, we evaluated the differences of properties in composite materials with different volume fractions using this system. We conclude that our technique is useful in the evaluation of erosion properties of composite materials.
Evaluation of wear resistance of thin hard coatings by a new solid particle impact test
Abstract For the evaluation of tribological properties of thin hard coatings, several experimental techniques are normally used, such as scratch testing and testing against abrasive, erosive, and sliding wear, and fretting. In this paper, we propose slurry jet, a new type of solid particle impact test, in order to quickly evaluate wear properties of thin, single layered or multilayered physical vapor deposited (PVD) coatings. By slurry jet 1 μm alumina particles were impacted at high velocity perpendicular to thin PVD coatings of TiN, TiN/NbN, TiN/TaN, TiN/CrN, TiN/TiAlN deposited on a high speed steel (HSS) substrate material. The coatings proved to have much higher erosion resistance than the substrate material and, consequently, the wear rate increased significantly to the higher level of the HSS material when the coatings were penetrated. The maximum peak-to-valley roughness (Ry) of the eroded coatings was of the order of 0.1–0.5 μm, suggesting that the size of the detached particles was of the same order. The ranking of erosion resistance and correlation to the mechanical properties, such as hardness and critical normal load obtained by scratch testing are discussed. We conclude that the proposed evaluation test is fast and easy to accomplish. It generates reproducible results and is very sensitive to the quality of the coating. Thus, it can preferentially be used as a screening test when evaluating coatings and coated materials. In particular, the interface strength of multilayered coatings with very thin lamella can be assessed. For the coatings included in this study, the TiN/TiAlN proved to have the highest erosion resistance, whereas the TiN/CrN was the worst.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.