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1.
Failure mode maps in the thin film scratch adhesion test 总被引:1,自引:0,他引:1
S.J. Bull 《Tribology International》1997,30(7):491-498
The scratch test has been used to assess thin coating adhesion for some time now. In this test a diamond indenter is drawn across the coated surface under an increasing load (either stepwise or continuous) until at some load, termed the critical load, Lc a well-defined failure event occurs; if this failure event represents coating detachment then the critical load can be used as a qualitative measure of coating-substrate adhesion. However, it is well known that a range of possible failure modes can occur and only some of these are dependent on adhesion. Other failure modes which depend on plastic deformation and fracture within the coating, rather than any adhesive failure at the coating substrate interface, may be just as useful in the assessment of coating quality particularly for tribological applications. In this paper the load regimes in which the main adhesion-related failure modes (spallation and buckling) occur as a function of coating thickness will be presented for thermally grown oxide and sputtered nitride coatings. The origin of the observed failure modes and the use of the scratch test to assess coating/substrate adhesion in a more quantitative fashion is discussed in the light of these observations. 相似文献
2.
Rachida Barkallah Rym Taktak Noamen Guermazi Fahmi Zaïri Jamel Bouaziz Fahed Zaïri 《The International Journal of Advanced Manufacturing Technology》2018,95(9-12):3369-3380
This paper focuses on the mechanical characterization of a bioceramic based on commercial alumina (Al2O3) mixed with synthesized tricalcium phosphate (β-TCP) and commercial titania powder (TiO2). The effect of β-TCP and TiO2 addition on the mechanical performance was investigated. After a sintering process at 1600 °C for 1 h, various mechanical properties of the samples have been studied, such as compressive strength, flexural strength, tensile strength, elastic modulus, and fracture toughness. The measurements of the elastic modulus (E) and the tensile strength (σ t ) were conducted using the modified Brazilian test while the compressive strength (σ c ) was determined through a compression test. Also, semi-circular bending (SCB) specimens were used to evaluate the flexural strength (σ f ) and the opening mode fracture toughness (K IC). From the main results, it was found that the best mechanical performance is obtained with the addition of 10 wt.% TCP and 5 wt.% TiO2. Alumina/10 wt.% tricalcium phosphate/5 wt.% titania composites displayed the highest values of mechanical properties and a good combination of compressive strength (σ c ?≈?352 MPa), flexural strength (σ f ?≈?98 MPa), tensile strength (σ t ?≈?86.65 MPa), and fracture toughness (K IC?≈?13 MPa m1/2). 相似文献
3.
Effect of elastic modulus mismatch on the contact crack initiation is investigated to find major parameters in designing desirable
surface-coated system. Silicon nitride coated soft materials with various elastic modulus mismatch,E
c
/E
s
= 1.06 — 356 are prepared for the analysis. Hertzian contact test is conducted for producing contact cracks and the acoustic
emission detecting technique for measuring the critical load of crack initiation. The implication is that coating thickness
and material strength are controllable parameters to prevent the initiation of contact cracks resulted from the elastic modulus
mismatch in the hard ceramic coating layer on the soft materials. 相似文献
4.
The ‘critical load' for wear particle generation of carbon nitride coatings sliding against a spherical diamond under a linearly increasing load has been examined in situ in relation to different nitrogen incorporation conditions, i.e. assisted N ion acceleration energy and N ion beam current density, and different coating thickness. An environmental scanning electron microscope (E-SEM), in which a pin-on-disk tribotester was installed, has provided direct evidence in situ of when, how and where wear particle generation occurs during the sliding of carbon nitride coatings against a spherical diamond. The in-situ examination of non-conductive carbon nitride coatings are available in E-SEM free from surface charging with controllable relative humidity. The sliding tests under linearly increasing load up to 300 mN at a sliding speed of 10 μm/s have been carried out with the purpose of measuring the ‘critical load' for wear particle generation in a similar way to the traditional macro scratch testing. However, instead of the ‘critical load', the critical maximum Hertzian contact pressure Pmax will also be used in the following for better understanding. Based on the systematic study of seven combinations of nitrogen incorporation parameters and five kinds of thickness (0, 10, 50, 100 and 200 nm), the applicable range of Pmax for wear particle generation can be increased from 1.6Y to 1.831.92Y or to 1.801.89Y, where Y is defined as the yield strength of silicon of 7 GPa, by coating carbon nitride onto silicon with changing nitrogen incorporation conditions of ion acceleration energy and ion current density, or varing coating thickness from 10 to 200 nm. It also appears that the observed wear particle generation of carbon nitride coatings was associated with a failure initiated in the silicon substrate rather than within the carbon nitride coating or at the coating–substrate interface in the light of both the empirical identification and the theoretical discussion. 相似文献
5.
B. Lamy 《Tribology International》1984,17(1):35-38
In static identation of brittle surfaces, fracture and deformation operate on a comparable scale. Kc/H governs the ductile or brittle nature of the contact, hence H/Kc is a convenient brittleness index. A pendular scratching test was developed which extends to dynamic contact analytical results pertaining to static identation: the objective was to establish investigative means necessary for the selection of semi-brittle, hard coatings subject to abrasive or erosive wear. Different semi-brittle surfaces were tested. A transition scratching depth from ductile to brittle abrasion was observed. the static brittleness index, Kc/H, is connected directly to this scratching transition depth. The pendular scratching test permits determination of Kc/H, and thereby the toughness, Kc, of hard coatings. Prediction of the morphology of surface scratching is possible using this brittleness index. Brittle scratch susceptibility can be related directly to poorer wear resistance. 相似文献
6.
The development of second phase zirconia precipitates in a beta-alumina matrix has been achieved using chemical reactions which occur during the firing process. The degree of success of each of several fabrication routes has been evaluated by use of toughness measurements and electron microscopy techniques. Approximately half of the routes yielded ~90% retention of tetragonal zirconia, resulting in an approximate doubling of the Mode 1 critical stress intensity factor (K1c). 相似文献
7.
This is the second paper of a two-part report. In the first paper, empirical data on the wear particle generation in carbon nitride coatings subjected to repeated sliding contact with a spherical diamond counter-face is reported. The effect of coating thickness on the wear particle generation is also discussed in the first paper. In this paper, a simplified theoretical expression, combining the Coffin-Manson equation with the analytical solution of a proposed elastic perfectly-plastic indentation model, is introduced. The expression successfully correlates critical number of friction cycles for wear particle generation Nc to coating thickness h, contact pressure P and radius of spherical asperity on the tip of the diamond pin R. With this expression, the lifespan of sliding components can be predicted.The theoretical results computed for diamond pin with a specific asperity radius value of 250 nm were compared with the experimental results reported in the first paper. The theoretical model successfully predicts the maximum lifespan of a component, Nc, in repeated sliding applications. The influences of various contact pressures and asperity radii on the maximum lifespan were also assessed using the model. 相似文献
8.
K. Liu X. P. Li M. Rahman X. D. Liu 《The International Journal of Advanced Manufacturing Technology》2004,24(5-6):321-326
In this paper, the cutting modes for grooving a tungsten carbide work material are investigated and presented. The grooving tests were carried out on an inclined workpiece surface using a solid CBN tool on a CNC lathe. The experimental results indicated that there was a transition from a ductile mode cutting to a brittle mode cutting in the grooving of tungsten carbide workpiece material as the depth of cut was increased from zero to a critical value. Ductile mode cutting is identified by the machined workpiece surface texture and the material removal ratio f
ab
-ratio of the average of the volume of material removed to the volume of the machined groove. Scanning electron microscopy (SEM) observations on the machined workpiece surfaces indicated that there are three cutting modes in the grooving of tungsten carbide as the depth of cut increased: a ductile mode, a semi-brittle mode and a brittle mode. The ductile cutting mode depends on the stress in the cutting region, i.e., whether or not the shear stress in the chip formation region is greater than the critical shear stress for the chip formation (
slip
>
c
), and whether or not the fracture toughness of the work material is larger than the stress intensity factor (K
1<K
c
). When (
slip
<
c
) and (K1>K
c
), crack propagation dominates, the chip formation and the cutting mode are brittle.Nomenclature
A
1
, A
2
A cross-section areas of the ridge
-
A
V
A cross-section area of the groove
-
A
W
The value of A
V
subtracted by A
1+A
2
-
F
X
The horizontal force
-
F
Z
The vertical force
-
K
C
The fracture toughness
-
K
I
The stress intensity factor
-
f
ab
The work material removal ratio
-
f
n
The normal cutting force
-
f
t
The tangential cutting force
-
The inclined angle
-
c
The critical shear stress for dislocation
-
slip
The shear stress in chip formation zone 相似文献
9.
Hao-Hao Ding Gaëtan Bouvard Jean Geringer Julien Fontaine Philippe Kapsa 《摩擦学汇刊》2013,56(6):1155-1172
AbstractThe influence of diamond-like carbon (DLC) coating positions—coated flat, coated cylinder, and self-mated coated surface tribopairs—on the fretting behaviors of Ti-6Al-4V were investigated using a fretting wear test rig with a cylinder-on-flat contact. The results indicated that, for tests without coating (Ti-6Al-4V–Ti-6Al-4V contact), the friction (Qmax/P) was high (0.8–1.2), wear volumes were large (0.08–0.1?mm3) under a large displacement amplitude of ±40 µm and small (close to 0) under a small displacement amplitude of ±20 µm, and the wear debris was composed of Ti-6Al-4V flakes and oxidized particles. For tests with the DLC coating, under low load conditions, the DLC coating was not removed or was only partially removed, Qmax/P was low (≤0.2), and the wear volumes were small. Under high load conditions, the coating was entirely removed, Qmax/P was high (0.6–0.8), and the wear volumes were similar to those in tests without coating. The wear debris was composed of DLC particles, Ti-6Al-4V flakes, and oxidized particles. The DLC coating was damaged more severely when deposited on a flat surface than when deposited on a cylindrical surface. The DLC coating was damaged more severely when sliding against a DLC-coated countersurface than when sliding against the Ti-6Al-4V alloy. 相似文献
10.
Generally the fretting fatigue S-N curve has two regions: one is the high cycle (low stress) region and the second is the low cycle (high stress) region. In a previous paper we introduced the fretting fatigue life estimation methods in high cycle region by considering the wear process; with this estimation method the fretting fatigue limit can be estimated to be the crack initiation limit at the contact edge. In this paper we estimate the low cycle fretting fatigue life based on a new critical distance theory, modified for a high stress region using ultimate tensile strength σB and fracture toughness KIC. The critical distance for estimating low cycle fretting fatigue strength was calculated by interpolation of the critical distance on the fretting fatigue limit (estimated from σw0 and ΔKth) with critical distance on static strength (estimated from σB and KIC). By unifying this low cycle fretting fatigue life estimation method with the high cycle fretting fatigue life estimation method, which was presented in the previous paper, we can estimate the total fretting life easily. And to confirm the availability of this estimation method we perform the fretting fatigue test using Ni-Mo-V steel. 相似文献
11.
Thin hard coatings in the thickness range of only a few micrometers deposited by physical vapour deposition (PVD) on components or tools can improve the friction and wear properties by several orders of magnitude. A 2 μm thick TiN (E=300 GPa) coating on a high-speed steel substrate with a bond layer at the interface between the coating and the substrate was modelled by micro-level three-dimensional finite-element method (3D FEM) in order to optimise a coated surface with regard to coating fracture. Both compliant low modulus (E=100 GPa) and stiff high modulus (E=500 GPa) bond layers at the coating/substrate interface of 200 and 500 nm thickness were investigated. First principal stresses were simulated for scratch test geometry in the load range of 7.5-15 N. Very high stress concentrations of above 5700 MPa tensile stresses were observed in the bond layer just behind the contact zone for the stiffer bond layer. The stiff bond layer generated 5 times higher tensile stress maxima compared to the compliant bond layer. There was approximately 3.5 times larger strain in the compliant bond layer compared to the stiff bond layer. The general coating design advice based on this exercise is that when a bond layer is used e.g. for coating/substrate adhesion improvement should the bond layer be less stiff than the coating not to generate high and critical tensile stresses. The thickness of the bond layer may vary and is not critical with respect to generated stresses in the surface. 相似文献
12.
The tribological performance of Al2O3/NiCr coating deposited on steel (SM45C) was investigated under lubrication. The parameters of sliding wear consist of normal
load and coating thickness. Test result showed that there was no evidence of an improved bonding strength in the coating.
However, the wear resistance of the Al2O3/NiCr coating was significantly greater than that of the Al2O3 coating. It was evident that the residual stress for the AI2O3 coating was higher than that of the Al2O3/NiCr coating from the scratch test failure of coating. The bond coating played an important role in decreasing the residual
stress. Also, it was found that the residual stress had a notable influence on the wear mechanism. 相似文献
13.
《Tribology - Materials, Surfaces & Interfaces》2013,7(4):219-224
AbstractThe bound model to determine coating toughness limits by nanoindentation tests was originally proposed by Toonder et al. However, the assumptions in this method conflict with each other. It provides lower and upper toughness limits for load control tests; however, it is unable to give the lower toughness limit for displacement control tests. In this paper, a modified model is presented by more comprehensive analysis of the unloading curves at the points where the crack starts and stops respectively. This modified method equally provides the lower and upper limits of fracture dissipated energy for both load control and displacement control. The model developed here has been successfully applied to fullerene like CNx coatings deposited on various substrates such as Si, SiC and Al2O3. It is also applicable to other coated systems provided that the through thickness fracture induced excursion is observed in the load–displacement curve. 相似文献
14.
We consider delamination crack growth controlled by gas diffusion into the crack. If the gas is accumulated inside the delamination, after some incubation period, the crack starts growing under the pressure of the accumulated gas. An important example is given by hydrogen-induced delamination. Hydrogen absorbed by a metal is typically dissolved in the proton form within the lattice. Some of the protons reach the surface of pre-existing or freshly created cracks or delaminations where they recombine with electrons and form molecular hydrogen in the crack cavity. Since the molecular form of hydrogen is thermodynamically more stable, this process leads to accumulation of hydrogen gas inside the delamination crack. Under the excessive hydrogen pressure fracture often takes place even in the absence of any additional external loading. It is especially dangerous if the metal is covered with coating, where because of the dissimilarity of materials, microscopic voids appear more frequently. This leads first to hydrogen precipitation within these coating–metal interface voids and then to their development. This results in the delaminating of the coating. As it is well known, in the absence of aggressive media the cracking resistance of a material is characterized by a unique constant: so that if the stress intensity factor is smaller than this constant, the crack is fixed, and if it is larger, the crack moves in a dynamic regime. But in the presence of aggressive media, particularly hydrogen, the crack development is characterized by a smooth kinetic function v(KI), which is dependence of the crack velocity on the stress intensity factor, with the lower threshold value of resistance Kscc smaller than the static critical stress intensity factor KIc. As numerically shown in the author's earlier work for the internal crack growth, the crack velocity first increases in accordance with the kinetic function, until reaching some value of vs, and remains at the same level afterwards. Since, as has been obtained by the author in the previous paper, kinetic equations for internal and delamination cracks are essentially identical, the same conclusion can be derived for the latter. In this paper the stability and asymptotic approach to the constant velocity of delamination growth is proved analytically. If vs is known, the corresponding value of the stress intensity factor, Ks, is obtained by substituting vs into the kinetic function v(KI). 相似文献
15.
Ouk Sub Lee Jae Chul Park Gyu Hyun Kim 《Journal of Mechanical Science and Technology》2000,14(7):752-763
The stress field around the dynamically propagating interface crack tip under a remote mixed mode loading condition has been studied with the aid of dynamic photoelastic method. The variation of stress field around the dynamic interface crack tip is photographed by using the Cranz-Shardin type camera having 106 fps rate. The dynamically propagating crack velocities and the shapes of isochromatic fringe loops are characterized for varying mixed load conditions in double cantilever beam (DCB) specimens. The dynamic interface crack tip complex stress intensity factors,K 1 andK 2, determined by a hybrid-experimental method are found to increase as the load mixture ratio of y/x (vertical/horizontal) values. Furthermore, it is found that the dynamically propagating interface crack velocities are highly dependent upon the varying mixed mode loading conditions and that the velocities are significantly small compared to those under the mode I impact loading conditions obtained by Shukla (Singh & Shukla, 1996a, b) and Rosakis (Rosakis et al., 1998) in the USA. 相似文献
16.
Due to strongly tribological atmosphere sensitivity of carbon-based coatings, it is of extreme significance to investigate their friction and wear behaviors in different atmospheres. In this letter, duplex nc-TiC/a-C(Al) nanocomposite carbon-based coating coupled with high hardness, low internal stress and high adhesion strength was successfully fabricated using magnetron sputtering process. The friction and wear behaviors of as-fabricated coating were evaluated in dry N2, humid N2, air, dry O2, and humid O2 atmospheres, respectively. Results show that the as-fabricated coating possesses very high friction and wear due to the strong covalent bond interactions at the sliding interface caused by the free ??-bonds on the coating surface in dry N2 atmosphere. Whereas the free ??-bonds can be efficiently terminated and passivated by water and/or oxygen molecules to weaken the strong covalent bond interactions to result in low friction and wear of coating in humid N2, air, dry O2, and humid O2 atmospheres. The compact and homogeneous carbonaceous tribo-layer on the counterpart is mainly responsible for the lowest friction and wear of coating in humid N2 atmosphere. Whereas the tribo-layer can be restrained to a certain extent by the tribo-chemical reaction, especially it results in a nearly negligible carbonaceous tribo-layer on the counterpart in dry O2 atmosphere, which is mainly responsible for largely increased friction and wear of coating. 相似文献
17.
Abrasive wear performance of carbon fabric reinforced polyetherimide composites: Influence of content and orientation of fabric 总被引:4,自引:0,他引:4
Dry abrasive wear performance of five plain weave carbon fabric (CF) reinforced Polyetherimide (PEI) composites, developed with increasing CF contents (in the step of 10 vol%) is reported in this paper. It was observed that composite reinforced with 65 vol% CF (IP65) exhibited the best tensile and shear strength and closely followed the leader (IP75) in flexural strength. IP65 when abraded against silicon carbide paper showed highest wear resistance (WR) and lowest friction coefficient (μ) among all composites. The composites IP85 and IP40 containing highest and lowest amount of CF respectively showed least enhancement in strength properties and poorest wear performance. Parallel studies on the influence of fabric orientation with respect to the sliding plane and direction, on WR showed that when CF was oriented parallel to the sliding plane, it had poorest wear resistance. The performance improved for the composites when fabric was oriented normal to the plane. The parallel or anti-parallel orientation of warp or weft fibers with respect to sliding direction showed marginal changes in friction and wear performance. Wear mechanisms were suggested and strongly supported by worn surface analysis using SEM.Efforts were also done to investigate the wear-property correlation. It was observed that the WR was directly proportional to the product of interlaminar shear strength (Is) and elastic modulus (E). Fairly good linearity was shown for specific wear rate (K0) as a function of factor (μP/IsE) where μ is coefficient of friction and P is the normal pressure (N/mm2). 相似文献
18.
Processing of agglomerated particulate products can lead to attrition by abrasive wear as the agglomerates move relative to one another. In order to investigate this damage mechanism under controlled conditions, bar-shaped silica sand agglomerates of a range of strengths have been formed by addition of appropriate proportions of polyvinylpyrrolidone binder (molecular weight 44 000). These were then tested for wear resistance against various grades of abrasive paper and by rubbing against each other. In common with many materials, it was found that the wear rate is proportional to total sliding distance and to normal load, and independent of relative velocity. A simple Coulombic interlocking wear model is advanced to account for the dependence of wear rate on the size of abrasive particle forming the countersurface. In sustained (multi-pass) sliding, the presence of the debris reduces the attrition rate significantly. This phenomenon has been exploited by various workers who introduced solid lubricants into particle-processing devices in order to reduce attrition. The wear rate of agglomerates of different strengths has been found to be approximately proportional to the reciprocal of Kc, the critical stress intensity factor measured for the same bar agglomerates using the three-point bend test. This relationship between attrition rate and Kc has also been found for attrition in fluidized beds. 相似文献
19.
Kwang Ho Lee Arun Shukla Venkitanarayanan Parameswaran Vijaya Chalivendra Jae Sug Hawong 《Journal of Mechanical Science and Technology》2002,16(2):165-174
In the present study, interfacial cracks between an isotropic and orthotropic material, subjected to static far field tensile
loading are analyzed using the technique of photoelasticity. The fracture parameters are extracted from the full-field isochromatic
data and the same are compared with that obtained using boundary collocation method. Dynamic photoelasticity combined with
high-speed digital photography is employed for capturing the isochromatics in the case of propagating interfacial cracks.
The normalized stress intensity factors for static cracks are greater when α=90° (fibers perpendicular to the interface) than
when α=0° (fibers parallel to the interface), and those when α=90° are similar to ones of isotropic material. The dynamic
stress intensity factors for interfacial propagating cracks are greater when α=0° than α=90°. For the velocity ranges (0.1<c/c
s1
<0.7) observed in this study, the complex dynamic stress intensity factor |K
D
|, I increases with crack speedc, however, the rate of increase of |K
D
| with crack speed is not as drastic as that reported for homogeneous materials. 相似文献
20.
The intermolecular interactions at the interface between monomolecular hydroxyl-terminated perfluoropolyether (PFPE) liquids
(Zdol, Zdol-TX, Z-Tetraol, Zdiac) and a sputtered amorphous silicon nitride film (SiNx) are investigated using contact angle goniometry, Fourier transform infrared spectroscopy, and ab initio computational chemistry. The results demonstrate that the adhesion between the PFPE liquids and the SiNx surface occur via the polar interactions between the PFPE end groups (-OH, -COOH) and the polar sites on the SiNx surface (e.g., SiOH). The attractive interactions lead to a lowering of the polar surface energy with increasing PFPE coverage
up to a monolayer. The binding energy is computed to be approximately −4 to −9 kcal/mol, depending upon the polarity of the
PFPE end group. Adsorbed water is shown to compete with PFPE for surface bonding sites on SiNx (−4.4 kcal/mol) that can lead to a significantly reduced level of adhesion for some of the hydroxyl-terminated PFPEs. A higher
level of adhesion between the PFPEs and SiNx can be attained by increasing the strength of the hydrogen bond and/or increasing the configurational entropy of the PFPE
end group to facilitate the hydrogen bonding reaction. 相似文献