Solid State Phenomena Vol. 331

Abstract: Plasma Spray Physical Vapour Deposition (PS-PVD) is one of the promising methods considered as an alternative to Electron Beam Physical Vapour Deposition (EB-PVD) process used for production of ceramic columnar layer for turbine blades protection against high temperature. The PS-PVD method enables to control the coating structure. In presented article the dense to columnar structure was formed during single-step PS-PVD process using yttria stabilized zirconia oxide (YSZ). The ceramic coating was deposited using LPPS-Hybrid (Oerlikon-Metco) system at Rzeszow University of Technology. The IN 713 alloy with aluminide coating produced by CVD method was used as a base material. The inner zone of the ceramic coating was characterized by dense structure and the outer was characterized by columnar structure. The influence of power current, gas composition flow, powder feed rate and coating time on thickness of both zones was investigated using Scanning Electron Microscopy method. The relationship between process parameters and thermal conductivity was also investigated using Laser Flash Method (LFA). Conducted experimental process showed that using of 1800A power current higher Ar flow (80 NLPM) as well as powder feed rate (30 g/min) enables to obtain dense structure of coating. When higher energy of plasma (power current 2200 A, plasma gasses flow (Ar-35 NLPM, He-60 NLPM) and lower powder feed rate was used the columnar zone was formed. The thickness of obtained coating was in range 140-200 μm. The formation of thick dense layer increased the overall thermal conductivity of coating in comparison with conventional columnar ceramic layer. The combination of thin 20 μm dense-zone with thick (120 μm) columnar zone reduces thermal conductivity of whole coating.

Abstract: This study reports the influence of Ni content on the structure and wear resistance of (Ti, Cr)C-based coatings. The (Ti,Cr)C-based composite powders, cladded with 18, 25 and 33 wt.% Ni were used to deposite coatings on stainless steel substrate by detonation spraying technique. The thickness of the coatings reaches 350-500 μm, the porosity is about 2%. The (Ti,Cr)C-Ni coatings have a dense lamellar microstructure with uniform distribution of refractory particles and metal binder. The wear behavior of the coatings against steel ring were investigated by dry sliding wear tests. Depending on the Ni content the sliding wear loss of the (Ti,Cr)C-based coatings was 1,2-2 times less than that of (Ti,Cr)C detonation-sprayed coating. The investigation of worn surfaces revealed that the wear mechanism of the (Ti,Cr)C-based coatings with Ni content increase changes from abrasive to oxidative.

Abstract: Materials based on cerium oxides and REE are perspective for use in medicine, energy and mechanical engineering due to the uniqueness of their authorities. Stationary system diagrams are the physicochemical basis for the creation of such materials as solid electrolytes for fuel comics, oxygen gas sensors, catalyst carriers, protected coatings for alloys, etc. In this work, phase equilibria and structural transformations in the system CeO₂-La₂O₃-Yb₂O₃ at a temperature of 1500 oС in all international concentrations are investigated by the methods of microstistructural and X - ray phase analysis. It is established that in the triple system CeO₂-La₂O₃-Yb₂O₃ fields of solid solutions based on cubic (F) modification of the structure of the structure of fluorite CeO₂, monoclinic (B) and cubic (C) modification of Yb₂O₃ and hexagonal (A) modification of La₂O₃ (R) are used, which crystallizes in a Perovski-type structure with rhombic curvatures. It was found that the rarefaction of CeO₂ in the crystal lattice of the ordered phase with the structure of the perovskite type LaYbO₃ (R) is ~ 3 mol. %. Isothermal review of the state diagram of the systems CeO₂-La₂O₃-Yb₂O₃ at reveals the presence of two three-phase (F + C + R), (A + R + F) and five two-phase (A + F), (A + R), (R + C), (F + R), (F + C) regions.

Abstract: The ultra-dispersive powders of pre-ceramic precursors for boron carbide based composites were obtained by relatively low-temperature (at 200 – 1000 °C) synthesis from liquid charges containing available compounds such as salts and oxides. Boron carbide matrix ceramics were compacted by their reactive spark plasma sintering (SPS) at 1500 – 1700 °C. It is noted that the X-ray diffraction (XRD) peaks corresponding (m)ZrO₂ and WC phases presented in the synthetic pre-ceramic precursors disappear after the SPS is conducted at 1500 °C. It is established that the addition of tungsten and cobalt compounds promotes both the low-temperature synthesis of ceramic components and sintering processes of their powders. Energy dispersive X-ray (EDX) analysis showed that the ceramics contain a small amount of Co (0.8 – 2 wt.%). The density of samples of cobalt-containing ceramics B₄C–ZrB₂–W₂B₅–Co is higher compared to that of cobalt-free ceramics B₄C–ZrB₂–W₂B₅.

Abstract: In this article are presented the results of X-ray and IR spectroscopic studies of the structure of the atmosphere - and chemically resistant composite materials based on medium density polyethylene. The presence of specific interactions with polyethylene ingredients in composite materials. It has revealed the appearance on the surface of the active radicals that promote increased interaction fillers with polyolefins, as well as the increase of the elastic-strength characteristics of composite materials are revealed.

Abstract: Bearings are important in moving machinery. Today machines are used in varied fields, including environments where metals are not ideal materials. Industrial polymers are a possible alternative due to their mechanical properties, and the thermoplastic polymer Polyether ether ketone (PEEK) is suitable in many varied conditions. The failure mechanisms of PEEK are not fully understood, so the purpose of this study is to continue examining the relationship between load and rotation speed in rolling contact fatigue of PEEK thrust bearings in water conditions, to evaluate fatigue strength and life.

Abstract: Bearing sleeve, as one of important parts of bearing structure, determine the bearing performance directly. In this paper, based on the ball joint structure, the tribological properties between Polyoxymethylene (POM) and 40Cr are studied with Ring-Block method. The effects of friction velocity and applied load on friction coefficient are tested and analysed, the analytical model in friction force, friction velocity and applied load are created, which will provide useful technical data to the application.

Abstract: To explore a new method to prepare B-doped silicon carbide, with B₂O₃ as a dopant, silicon dioxide and graphite as raw materials, B-doped silicon carbide (B_xSi_1-xC) was prepared using pressure-free sintering and self-spreading combustion methods. The material phase, microstructure, particle size, compressive strength and bulk density were characterized by the XRD, SEM, laser granularity tester, particle strength tester and powder comprehensive characteristic tester. The results show that the doping of B can inhibit the growth rate of the product, with the optimal ratio of SiO₂:C:B₂O₃=60:120:150. At the same time, the crystal type of the generated product B_xSi_1-xC is relatively complete. The D₅₀ is 17.3 μm, its bulk density is up to 1.08 g^-1cm^-3, and its single particle compression strength is second only to diamond, much higher than that of ordinary SiC.

Abstract: Al₂O₃ fiber has high temperature resistance, chemical corrosion resistance, and low density. It is a good thermal insulation material. Reed is one of the most widely distributed angiosperms. The short cilia of the reed have a hollow structure, which can improve the thermal insulation performance of the fiber. Using reed fibers as a biological template, Al₂O₃ fibers with a hollow structure were prepared. After the reed fibers were immersed in the precursor solution, they were dried and sintered at a high temperature to obtain Al₂O₃ hollow fibers. The fibers replicated the hollow structure and the excellent continuity of the reed fibers.

Abstract: In view of the low performance of porous ceramics on the wall, the heavy task of saving clay resources, and the major problems of dredging the Yangtze River, this thesis uses low-grade quartz sand along the Yangtze River as the main raw material and kaolin as the plasticizer. Drying, sintering and other processes prepare high-performance porous quartz ceramics, and improve the performance of porous quartz ceramics by studying the control conditions and the control mechanism related to the performance of the sintered body. Quartz porous ceramic bodies were sintered at 1100 °C and 1200 °C, and no obvious gradient structure was found. However, the quartz porous ceramic bodies had obvious gradient structures after sintering at 1300°C. The quartz porous ceramic bodies were sintered. When the temperature is 1400 °C, the green body is not found to have a pore gradient structure. When the water-to-material ratio is 1.2 and 1.3, the quartz porous ceramic body has no obvious gradient structure; when the water-to-material ratio is 1.4, 1.5, the sample has an obvious gradient structure. Combining the cost performance between material performance and energy consumption, in order to obtain a better bonding point, porous silica ceramics should be prepared with a water-to-material ratio of 1.4 and a sintering temperature of 1300 °C to prepare porous silica ceramics with a better pore gradient structure. Its porosity is 32.45%, and its compressive strength is 5.23 MPa.