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1.
Silicon nitride (Si3N4) cutting tools exhibit excellent thermal stability and wear resistance in the high-speed machining of cast irons, but show
poor chemical wear resistance in the machining of steel. Conventional chemical vapour deposition (CVD) coating of Si3N4 tools has not been very successful because of thermal expansion mismatch between coatings and the substrate. This problem
was overcome by developing a CVD process to tailor the interface for titanium carbide (TiC) and titanium nitride (TiN) coatings.
Computer modelling of the CVD process was done to predict which phases would form at the interface, and the results compared
with analyses of the interface. Three Si3N4 compositions were considered, including pure Si3N4, Si3N4 with a glass phase binder, and Si3N4 + TiC composite with a glass phase binder. Results of machining tests on coated tools show that the formation of an interlayer
provides superior wear resistance and tool life in the machining of steel as compared to uncoated and conventionally coated
Si3N4 tools. 相似文献
2.
T. Amano B. J. Beaudry K. A. Gschneidner Jr. F. C. Laabs 《Journal of Materials Science》1989,24(11):3831-3836
The use of ZrO2 paints to coat SiGe materials used in radioisotopic thermoelectric generators was studied. The best results were obtained when the SiGe alloys were double coated with a 200 h anneal at 1000° C after each coating. The thermoelectric properties of these coated samples were about the same as for the SiGe alloys coated by SiO2 or Si3N4. The vapoursupression properties of the best ZrO2 coatings fell between those of SiO2 and Si3N4. In the SiGe doped with GaP alloys, the interface between the oxide coating and alloy is enriched with Ga2O3. 相似文献
3.
High Temperature Behavior of Si3N4 and Yb2SiO5 Coated Carbon Fibers for Silicon‐Nitride CMC
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For oxide‐free ceramic matrix composites (CMC), with Si3N4 matrix and carbon fiber reinforcement, for extreme high temperature applications, protective coatings of the C‐fibers are investigated. Two different coatings are compared: reactive CVD‐derived pure Si3N4 coatings to investigate C‐fiber‐matrix reactions and powder based Yb‐silicate coatings to reveal potential reactions with the Yb‐silicate additive serving as sintering aid for Si3N4. The reactivity toward carbon in nitrogen atmosphere is studied in the temperature interval from 20 °C up to 1700 °C. A new ceramic phase – an Yb‐carbido‐nitiridosilicate, Yb2Si4CN6–is found as product of carbothermal reduction of the Yb‐silicate. The carbothermal reduction occurs also with other RE‐silicates, RE = Yb, Er, Y, Gd, and Sm while SiC is found as reaction product on carbon fibers coated with pure Si3N4. The oxidation resistance of the coated fibers in air was investigated in the temperature interval up to 1000 °C, and the apparent activation energy of oxidation was analyzed based on DTA‐EGA results. The oxidation kinetic reveals a significant increase of onset point of oxidation temperature by up to 150 K for Si3N4 coated short carbon fibers obtained from the reactive CVD coating process. Such fibers have a high application potential for carbon‐fiber reinforced Si3N4‐CMC. The role of Yb2Si4CN6 as reinforcement for Si3N4‐CMC is discussed based on bond strength comparison of carbides (SiC), nitride silicates (SiAlON), and nitrides (Si3N4). 相似文献
4.
5.
《Materials Letters》2005,59(14-15):1897-1901
Powder coating has been explored as a method of incorporating sintering additives into a ceramic powder. This procedure has been explored in the case of Si3N4 powders coated with thin layers of MgO.The effectiveness of the powder coating technique has been evaluated by comparing the powder properties, densification behaviour, microstructure and mechanical properties of coated Si3N4 powders with identical powders in which the additive oxide has been added in particulate form. It is concluded that the powder coating technique is an excellent method of homogeneously incorporating minor amounts of sintering additive into a powder. The coated powder exhibited improved homogeneity, and gave good green compact density, high green strength, and faster densification rate. Moreover, coated powders densified more easily by pressureless sintering and showed a more homogeneous microstructure, higher strength and faster densification rates, compared with materials prepared using mixed oxide powders. Significant improvements in hardness and fracture toughness were observed for the coated powders. 相似文献
6.
Nobuya Iwamoto Norimasa Umesaki Shigeki Endo Toshiro Morimura 《Journal of Materials Science》1987,22(3):1113-1119
We have strengthened plasma-sprayed alumina coatings by incorporating SiC or Si3N4 whiskers. As a result, we found that the whisker-reinforced coatings were greatly improved in properties such as thermal shock resistance and adhesion. Major features of the plasma-sprayed Al2O3–5.0 wt % Si3N4, coating were investigated by means of scanning electron microscopy, secondary ion mass spectroscopy, X-ray diffraction, X-ray fluorescence spectroscopy and thermal radiation measurements. 相似文献
7.
Katja Myllymaa Sami Myllymaa Hannu Korhonen Mikko J. Lammi Hanna Saarenpää Mika Suvanto Tapani A. Pakkanen Virpi Tiitu Reijo Lappalainen 《Journal of materials science. Materials in medicine》2009,20(11):2337-2347
The adhesion and contact guidance of human primary osteogenic sarcoma cells (Saos-2) were characterized on smooth, microstructured
(MST) and micro- and nano-structured (MNST) polypropylene (PP) and on the same samples with a silicon-doped carbon nitride
(C3N4-Si) coating. Injection molding was used to pattern the PP surfaces and the coating was obtained by using ultra-short pulsed
laser deposition (USPLD). Surfaces were characterized using atomic force microscopy and surface energy components were calculated
according to the Owens-Wendt model. The results showed C3N4-Si coated surfaces to be significantly more hydrophilic than uncoated ones. In addition, there were 86% more cells in the
smooth C3N4-Si coated PP compared to smooth uncoated PP and 551%/476% more cells with MST/MNST C3N4-Si coated PP than could be obtained with MST/MNST uncoated PP. Thus the adhesion, spreading and contact guidance of osteoblast-like
cells was effectively improved by combining surface texturing and deposition of osteocompatible C3N4-Si coating. 相似文献
8.
Thermal stability of the TiAlN/Si3N4 nanoscale multilayered coating that was reported to show excellent hardness and toughness, has been investigated in terms of the nano-layered structure and hardness. TiAlN/Si3N4 nanoscale multilayered coatings with various thickness of Si3N4 layer were prepared by alternating deposition of TiAlN and Si3N4. In contrast to other nanoscale multilayered coating system such as AlN/CrN in which the intensity of the low angle XRD peaks decreases with increasing annealing temperature by interdiffusion between adjacent layers, the low angle XRD peak intensity of the nanoscale multilayered TiAlN/Si3N4 coatings increased after heat-treatment in an N2 atmosphere up to 800 °C. Such a thermal stability of the nano-layered structure is believed to be due to spinodal type phase separation of TiAlN and Si3N4, which increased the hardness value of the TiAlN/Si3N4 coating at high temperatures. 相似文献
9.
Xiaozhen Zhang Jianer Zhou Jiandong Wang Yuahua Jiang 《Journal of Materials Science》2009,44(11):2938-2944
Ca0.3Mg0.2Zr2(PO4)3 coating was deposited on the mullite ceramic to improve its alkali corrosion resistance at high temperatures, using sol–gel
method and dip-coating technique. The phase composition and microstructure of the coating were characterized by X-ray diffraction
and scanning electron microscopy (SEM). Results show that homogeneous, dense and single-phase Ca0.3Mg0.2Zr2(PO4)3 coating was successfully deposited on mullite ceramics. SEM microstructural examination revealed the excellent bonding between
Ca0.3Mg0.2Zr2(PO4)3 coating and mullite ceramics. The effectiveness of the prepared coating to improve the alkali corrosion resistance of mullite
ceramics was assessed through the measurements of mass loss and flexural strength degradation after 96 h and longer exposure
time at alkali corrosion condition at 1000 °C. A significant enhancement of the alkali corrosion resistance for Ca0.3Mg0.2Zr2(PO4)3-coated mullite samples was observed. Therefore, the effectiveness of the Ca0.3Mg0.2Zr2(PO4)3 material as protection coating for mullite ceramic is confirmed. 相似文献
10.
Cu–Si3N4 composite coatings were prepared by electrolysis from a copper sulphate solution containing dispersed Si3N4 particles of 0.4 or 1 μm mean size. Wear behavior of Cu–Si3N4 composite and pure copper coatings were evaluated using a pin-on-disc test machine under dry condition sliding. Effects of current density and particle concentration on the incorporation percentage of Si3N4, the preferred orientation of copper crystallites, the microstructure, the microhardness and the wear resistance of the coatings were determined. Si3N4 particles in the copper matrix resulted in the production of composite deposits with smaller grain sizes and led to change the preferred orientation growth from [1 0 0] to [1 1 0]. It was proved that the presence of Si3N4 particles decreases the wear loss and the friction coefficient of the coating. According to the results, the friction coefficient decreased dramatically from 0.52 to 0.26 for pure copper coatings to 0.16–0.24 for Cu–Si3N4 composite coatings. In addition, fluctuation of friction coefficient values for Cu–Si3N4 composite coating was lower compared with the pure copper coating. The wear properties of Cu–Si3N4 composite coatings were shown to depend on the weight fraction, the size and the distribution of co-deposited particles. 相似文献
11.
The development of modern technology requires metallic materials with better surface properties. In the present investigation; Si3N4-reinforced nickel nanocomposite coatings were deposited on a mild steel substrate using pulse current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of Ni and Ni–Si3N4 nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of Si3N4 particles in the Ni nanocomposite coating on the micro hardness, corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon nitride particles were obtained and the crystal grains on the surface of Ni–Si3N4 composite coating are compact. The crystallite structure was face centred cubic (fcc) for electrodeposited nickel and Ni–Si3N4 nanocomposite coatings. The micro hardness of the composite coatings (720 HV) was higher than that of pure nickel (310 HV) due to dispersion-strengthening and matrix grain refining and increased with the increase of incorporated Si3N4 particle content. The corrosion potential (E corr) in the case of Ni–Si3N4 nanocomposite had shown a negative shift, confirming the cathodic protective nature of the coating. 相似文献
12.
G. Willmann 《Advanced Engineering Materials》2001,3(3):135-141
The requirements for materials to be used for bearing surfaces in joint replacement are corrosion resistance in the body environment, reliability, hardness, and stiffness. Most important is coverage of the bearing surface with a stable oxide layer, so that the articulating surfaces can be lubricated by the synovial fluid. The synovial fluid, being a protein, can degenerate during frictional heating. This can be avoided if the materials used for wear couples have very good thermal conductivity. Bioceramics for joint replacement have been used since the 1970s. Alumina ceramics reduce the wear rate and solve the problem of implant loosening (osteolysis). Although the in vivo fracture rate for alumina parts is very small, further improved reliability is demanded. Alternative materials may be non‐oxide ceramics, zirconia ceramics, or hard coatings on metals. Advanced non‐oxide ceramics, such as SiC and Si3N4, are not suitable for bearing surfaces in knee‐ and hip‐joint replacement because the surface oxide formed is SiO2, which chips off. Y‐TZP zirconia does not have adequate phase stability. All hard coatings tried hitherto (TiN, DLC) have not been good enough. Alumina matrix composite (AMC) is a new type of bioceramics. AMC offers excellent tribological properties, no frictional heating, improved mechanical strength and fracture toughness, thus more in vivo reliability. So far test results have been very promising. 相似文献
13.
《Materials Science & Technology》2013,29(9):1132-1134
AbstractA SiC coating was prepared on the surface of a carbon fibre reinforced BN–Si3N4 composite by chemical vapour deposition. The coating was characterised by SEM and XRD, and the ablation behaviours of the coated and uncoated composites were investigated and compared. The coating is mainly amorphous SiC and quite compact; the ablated area of the composite is reduced considerably by the coating and the coated composite presents a lower linear ablation rate of 21˙4% and a lower mass ablation rate of 51˙6%. The SiC coating covers over the pores on the surface of the ablative composite, which prevents the flame from spreading to other regions and from penetrating the inside of the composite. As a result, both the chemical erosion and the mechanical denudation are restrained and the ablation resistance of the composite is improved. 相似文献
14.
CrAlSiN nanocomposite thin films with varying film chemistry were developed on tungsten carbide (WC) specimens using cylindrical cathodic arc physical vapor deposition (c-CAPVD) technique. The physical, mechanical, and tribological properties of all the films were comprehensively investigated for arriving at the film chemistry leading to the best properties with respect to mechanical applications. The best tribo-mechanical properties were obtained in films with Cr/(Al+Si) ratio of 1.2. This coating with best properties was translated on to WC drill bits for machining tests. The Al and Si content has shown major influence on the adhesion strength and phase constitution of the films, with a considerable change in residual stress too. The superior properties achieved could be attributed to the formation of a near-perfect nanocomposite structure, with the crystalline CrAlN phase surrounded by an amorphous Si3N4 phase. The tool life of the coated CrAlSiN tools was investigated during dry machining of EN 24 material. In comparison to the tool life of an uncoated tool and a TiAlSiN-coated tool, the best CrAlSiN coatings synthesized in this study performed exceedingly well. The present study clearly demonstrates the advantages of CrAlSiN over other existing similar coatings for high-speed machining. 相似文献
15.
The formation of ZrO2 and ZrO2-Y2O3 coatings from hydrous metal oxide sols on Nicalon NLM 202 silicon carbide fibers is investigated in detail. The results indicate that the microstructure of the oxide layer and the surface morphology of the coatings depend on the physicohemical properties of the sol. Kinetic studies of the oxidation of uncoated and coated fibers at different Y2O3 contents demonstrate that the oxidation rate of silicon carbide fibers decreases with increasing coating thickness. The effect of oxidation on the phase composition of Nicalon cloth samples coated with ZrO2 and ZrO2-Y2O3 is examined. 相似文献
16.
Hydrogenated diamond-like carbon (DLC) (H-DLC), argon-incorporated DLC (Ar-DLC) and nitrogen-incorporated DLC (N-DLC) coatings were deposited on flat rectangular Ti-6Al-4V samples. The DLC coatings were characterised by Raman spectroscopy and nanoindentation. Fretting wear tests were conducted on uncoated and DLC coated samples with an alumina ball as the counterbody. As the Ar-DLC and N-DLC coatings had relatively more sp2 network compared to the H-DLC coating, they exhibited lower values of hardness and elastic modulus. At both loads of 4.9 N and 14.7 N, all DLC coated specimens showed lower values of tangential force coefficient (TFC), wear volume and specific wear rate compared to the uncoated samples. While the Ar-DLC coated sample exhibited the lowest TFC, wear volume and specific wear rate at 4.9 N load, the N-DLC coated specimen exhibited the lowest TFC, wear volume and specific wear rate at 14.7 N load. 相似文献
17.
《Materials at High Temperatures》2013,30(3):305-316
AbstractThermal barrier coatings (TBCs) of yttria partially stabilized zirconia were deposited on gamma TiAl samples using electron-beam physical vapour deposition. The specimens were coated with intermetallic Ti –Al – Cr layers and CrAlYN/CrN nanoscale multilayer coatings. The lifetime of the TBC systems was determined performing cyclic oxidation tests in air at temperatures between 850 and 950–C. The TBC systems with Ti –Al – Cr and CrAlYN/CrN layers did not fail at 850 and 900–C during the maximum exposure time period of 1000 cycles of 1 h dwell time at high temperature. No spallation of the thermal barrier coatings was observed. As revealed by post-oxidation microstructural analysis, the protective coatings were severely degraded when exposed at 900–C, resulting in growth of mixed oxides on the substrate. Underneath the thermal barrier coating an outer oxide scale with a columnar structure was observed, consisting of rutile and α-Al2O3. Energy-dispersive X-ray spectroscopy analysis revealed zirconia and chromia being dissolved in the outer oxide scale. The columnar structure and the presence of zirconia indicated an effect of the TBC on the morphology of the outer oxide scale. The zirconia top coat exhibited an excellent adherence to this oxide scale formed on the protective layers when degraded, and at defects like cracks. When thermally cycled at 950–C, the TBC system on specimens coated with Ti –Al – Cr failed by spallation of the thermally grown mixed oxides, whereas the thermal barrier coating was well adherent to the outer oxide scale at this temperature, too. 相似文献
18.
《Materials Research Bulletin》2006,41(4):847-860
This paper addresses the structural characteristics and phase transformation behaviour of plain electroless Ni–P coating and electroless Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings. The X-ray diffraction patterns of electroless Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings are very similar to that of plain electroless Ni–P coating, both in as plated and heat-treated conditions. Selected area electron diffraction (SAED) patterns obtained on the Ni–P matrix of Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings exhibit diffuse ring patterns resembling the one obtained for plain electroless Ni–P coating. Phase transformation behaviour studied by differential scanning calorimetry (DSC) indicates that the variation in crystallization temperature and the energy evolved during crystallization of plain electroless Ni–P coating and electroless Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings is not significant. The study concludes that incorporation of Si3N4, CeO2 and TiO2 particles in the Ni–P matrix does not have any influence on the structure and phase transformation behaviour of electroless Ni–P coatings. 相似文献
19.
M. R. Mucalo N. B. Milestone I. C. Vickridge M. V. Swain 《Journal of Materials Science》1994,29(17):4487-4499
Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) has indicated that adherent crack-free coatings of amorphous SiC and Si3N4/Si2N2O can be built up on planar alumina substrates by pyrolysis of layers of polycarbosilane (PCS) and poly(diphenyl)silazane (PDPS) precursors applied by spin- or dip-coating methods. In general, multilayers of black SiC can be prepared by pyrolysis of PCS layers at 1100°C in a nitrogen atmosphere while transparent coatings consisting of multiple layers of Si3N4 are prepared by pyrolysis of either PCS or PDPS layers in a flowing atmosphere of ammonia at 1100°C. The Si3N4/Si2N2O layers prepared by pyrolysing spin-coated layers of PDPS layers are found to be superior in quality (with respect to blemishes and embedded debris) than those prepared from spin-coated layers of PCS. Microhardness tests reveal that the coatings derived from PCS and PDPS are significantly softer than would be expected for SiC and Si3N4. X-ray photoelectron studies reveal that the surface of the PCS-derived SiC coatings consists of an SiO2 layer while the surface of the PDPS-derived Si3N4/Si2N2O coating consists of an oxygen-rich silicon oxycarbonitride. These results are also generally supported by Rutherford backscattering spectra which also indicate considerable phase mixing of silicon, carbon, oxygen and nitrogen components within the bulk of the SiC and Si3N4/Si2N2O coatings on alumina. 相似文献
20.
《材料科学技术学报》2019,35(12):2767-2771
In order to modify the interface, SiON coating was introduced on the surface of silicon nitride fiber by perhydropolysilazane conversion method. Si3N4f/SiO2 and Si3N4f/SiONc/SiO2 composites were prepared by sol-gel method to explore the influence of SiON coating on the mechanical properties of composites. The results show that with the protection of SiON coating, Si3N4 fiber enjoys a strength increase of up to 24.1% and Si3N4f/SiONc/SiO2 composites have a tensile strength of 170.5 MPa and a modulus of 26.9 GPa, respectively. After 1000 °C annealing in air for 1 h, Si3N4f/SiONc/SiO2 composites retain 65.0% of their original strength and show a better toughness than Si3N4f/SiO2 composites. The improvement of mechanical properties is attributing to the healing effect of SiON coating as well as its intermediate coefficient of thermal expansion between Si3N4 fiber and SiO2 matrix. 相似文献