Effects of Composition and Surface Finish of Silicon Nitride Tappet Inserts on Valvetrain Friction

1999 ◽  
pp. 635-644 ◽  
Author(s):  
Amp Gangopadhyay ◽  
Douglas Mc Watt ◽  
Pierre Willermet ◽  
Gary M. Crosbie ◽  
Richard L. Allor
Keyword(s):  
Silicon Nitride ◽  
Surface Finish

scholarly journals Polishing of Silicon Nitride Ceramic Balls by Clustered Magnetorheological Finish

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 304
Author(s):  
Xiao-lan Xiao ◽  
Guang-xian Li ◽  
Hai-juan Mei ◽  
Qiu-sheng Yan ◽  
Hua-tay Lin ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Analytical Model ◽  
Surface Finish ◽  
Experimental Results ◽  
Machined Surface ◽  
Silicon Nitride Ceramic ◽  
Ceramic Ball ◽  
Contact Points ◽  
Micro Morphology ◽  
Improve Surface Finish

In this study, a novel finishing method, entitled clustered magnetorheological finish (CMRF), was proposed to improve surface finish of the silicon nitride ( Si 3 N 4 ) balls with ultra fine precision. The effects of different polishing parameters including rotation speeds, eccentricities and the machining gaps on surface finish of Si 3 N 4 balls were investigated by analyzing the roughness, sphericity and the micro morphology of the machined surface. The experimental results showed that the polishing parameters significantly influenced the surface finish. The best surface finish was obtained by using the polishing parameters: the machining gap of 0.8 mm, the eccentricity of 10 mm and the rotation ratio of 3/4. To further investigate the influence of the polishing parameters on the surface finish, an analytical model was also developed to analyze the kinematics of the ceramic ball during CMRF process. The resulting surface finish, as a function of different polishing parameters employed, was evaluated by analyzing the visualized finishing trace and the distribution of the contact points. The simulative results showed that the distribution and trace of the contact points changed with different polishing parameters, which was in accordance with the results of experiments.

EFFECT OF SURFACE FINISH ON FATIGUE STRENGTH IN SILICON NITRIDE

1992 ◽  
pp. 371-376
Author(s):  
M. TAKAHASHI ◽  
Y. MUTOH ◽  
K. YANAGI ◽  
H. OKAMOTO ◽  
T. OIKAWA
Keyword(s):  
Silicon Nitride ◽  
Fatigue Strength ◽  
Surface Finish ◽  
Effect Of Surface

Development and Testing of High Temperature Silicon Nitride Microturbine Rotors

2008 ◽  
Author(s):  
Vimal Pujari ◽  
Ara Vartabedian ◽  
Gregg Wayman
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Gas Turbine ◽  
Surface Finish ◽  
Systems Approach ◽  
Cutting Tools ◽  
High Yield ◽  
Machining Parameters ◽  
Dimensional Control ◽  
Machined Surface

Development and testing of gas turbine quality high temperature silicon nitride (NT154) components will be described. An advanced CNC green (using pressed powder blanks prior to densification) machining based complex shape forming methodology has been developed and successfully deployed to fabricate gas turbine quality rotor, vane ring and shroud components to net shape with high yield and required dimensional tolerances. Utilizing a systems approach involving green blank properties, type of cutting tools and machining parameters, the process has been optimized to achieve required as machined surface finish, dimensional control and part integrity. Integral bladed micro turbine rotors (IBR) and vane rings have been fabricated with dimensional control within 100 microns, surface finish within 1–2 microns. IBRs so formed have been successfully spin tested at room temperature at 40% above designed speed approaching maximum stress in the vicinity of 400 MPa.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

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