METHOD FOR TESTING A CERAMIC COMPONENT

Abstract

A method for testing a ceramic component for a fracture toughness includes changing the temperature of the component to a first temperature, for example, by heating the component, and changing the temperature of the component to a second temperature, for example, by cooling the component and testing the component for cracks. The temperature difference between the first temperature and the second temperature is determined based on a minimum fracture toughness.

Claims

1. A method for testing a ceramic component for a fracture toughness, comprising: changing the temperature of the component to a first temperature; and changing the temperature of the component to a second temperature; wherein a temperature difference between the first temperature and the second temperature is determined based on a minimum fracture toughness; and testing the component for cracks.

2. The method according to claim 1, wherein a value for the minimum fracture toughness is taken from a table.

3. The method according to claim 1, wherein the measured fracture toughness is at most +/−10% of a minimum required fracture toughness.

4. The method according to claim 1, wherein the fracture toughness is determined based on: TABLE-US-00002 h.sub.f = 75000 Wm.sup.−2K.sup.−1 h.sub.f = 100000 Wm.sup.−2K.sup.−1 Bi K.sub.surv K.sub.frac Bi K.sub.surv K.sub.frac — MPa m.sup.1/2 MPa m.sup.1/2 — MPa m.sup.1/2 MPa m.sup.1/2 Set 1, D = 12.7 mm, HK10 22.0 5.3 ± 0.3 5.5 ± 0.3 29.3 5.7 ± 0.3 5.9 ± 0.3 Set 2, D = 5.55 mm, HK10 10.2 5.5 ± 0.3 5.9 ± 0.3 13.7 6.0 ± 0.3 6.4 ± 0.3 Set 3, D = 5.55 mm, HK7 10.6 5.7 ± 0.1 6.0 ± 0.2 14.2 6.2 ± 0.1 6.5 ± 0.2

5. The method according to claim 1, wherein testing the component for cracks comprises applying a black dye to the component.

6. The method according to claim 1, further comprising determining a fracture toughness of a test component that corresponds to the ceramic component in shape, size, and material.

7. A ceramic component, manufactured using the method according to claim 1.

8. The ceramic components according to claim 7, wherein the ceramic component comprises more than 50% by weight of the material Si.sub.3N.sub.4, SiAlON, SiC, Al.sub.2O.sub.3, ZrO.sub.2, or of their mixtures.

9. The ceramic components according to claim 7, wherein the ceramic component has a fracture toughness that is greater than or equal to 4 MPa√m.

10. The ceramic components according to claim 7, wherein the ceramic component has a roughness at least sectionally on its surface that is less than 15 μm.

11. The method according to claim 1, wherein changing the temperature of the component to the first temperature comprises heating the component and wherein changing the temperature of the component to the second temperature comprises cooling the component.

12. The method according to claim 1, wherein the measured fracture toughness is at most +/−10% of a minimum required fracture toughness, wherein the fracture toughness is determined based on: TABLE-US-00003 h.sub.f = 75000 Wm.sup.−2K.sup.−1 h.sub.f = 100000 Wm.sup.−2K.sup.−1 Bi K.sub.surv K.sub.frac Bi K.sub.surv K.sub.frac — MPa m.sup.1/2 MPa m.sup.1/2 — MPa m.sup.1/2 MPa m.sup.1/2 Set 1, D = 12.7 mm, HK10 22.0 5.3 ± 0.3 5.5 ± 0.3 29.3 5.7 ± 0.3 5.9 ± 0.3 Set 2, D = 5.55 mm, HK10 10.2 5.5 ± 0.3 5.9 ± 0.3 13.7 6.0 ± 0.3 6.4 ± 0.3 Set 3, D = 5.55 mm, HK7 10.6 5.7 ± 0.1 6.0 ± 0.2 14.2 6.2 ± 0.1 6.5 ± 0.2 and, wherein testing the component for cracks comprises applying a black dye to the component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The Figures thus schematically show the following views.

[0033] FIG. 1 shows a schematic depiction of a method for testing a ceramic component according to an exemplary embodiment;

[0034] FIG. 2a shows a schematic depiction of a component according to an exemplary embodiment; and

[0035] FIG. 2b shows a schematic depiction of a component according to a further exemplary embodiment.

DETAILED DESCRIPTION

[0036] In the following description of the accompanying Figures, like reference numbers refer to like or comparable components. Furthermore, summarizing reference numbers are used for components and objects that appear multiple times in an exemplary embodiment or in an illustration, but that are described together in terms of one or more common features. Components or objects that are described with the same or summarizing reference numbers can be embodied identically, but also optionally differently, in terms of individual, multiple, or all features, their dimensions, for example, as long as the description does not explicitly or implicitly indicate otherwise.

[0037] FIG. 1 shows a method 1 for testing a ceramic component for a fracture toughness. For this purpose in a first step 2 the component is heated or cooled to a first temperature. In a second step 3 the component is subsequently heated or cooled to a second temperature. A temperature difference between the first temperature and the second temperature is determined here based on a minimum fracture toughness. In a third step 4 the component is tested for fracture toughness.

[0038] In some exemplary embodiments the component can be heated at the first temperature until the heated regions or the entire component homogeneously has the first temperature. The component can subsequently be rapidly cooled. In some exemplary embodiments simple geometric framework conditions for calculating the temperature difference can thereby be obtained. Alternatively the setting of a constant or homogeneous first temperature in the component to be tested can be omitted. For example, only the surface or an edge layer can be heated to the first temperature and subsequently quickly cooled.

[0039] In exemplary embodiments wherein the thermal shock treatment or the test method is comprised of a rapid heating, i.e., the first temperature is lower than the second temperature, a homogeneous heating and cooling of the components or only a heating and cooling of the edge layers can be carried out. A rapid heating can be selected, for example, with components wherein in an operation internal tensile stresses can occur that can lead to a compressive stresses in an outer region. With components wherein only one point especially loaded in use is to be tested, only this point of the component may possibly be treated with the first temperature and then the second temperature. For example, a zonal rapid heating can be effected using a powerful laser.

[0040] Different approaches can be chosen to detect the cracks in the third step 4. In principle the cracks can be detected in any manner, for example, acoustically, by vibration analysis, or optically. Cracks that do not extend to the surface can be detected, for example, by ultrasound or X-rays.

[0041] For an optical testing the cracks can possibly be made recognizable using a crack-penetrating dye. Here the component to be tested is immersed in a dyed, for example, black, liquid, for example, printer dye. The dyed liquid remains in the cracks after removal of the body from the liquid. It can possibly also be a fluorescent crack-penetrating dye. The cracks can then be made visible, for example, under ultraviolet light. No matter by which method the cracks are detected, components that have cracks that exceed at least one threshold value can be eliminated.

[0042] The method according to exemplary embodiments can be suited, for example, to be used in a running production. For this purpose it can be provided that the components are heated during the production processes to the first temperature. For this purpose, for example, a conveyor can be provided, using which the component is transported through the oven. The ceramic component can subsequently be guided using the conveyor to a quenchant in order to be cooled to the second temperature. A liquid, for example, water or oil, is suitable as quenchant, for example. Furthermore a gas can also be used as quenchant. With a quenching with gas the gas can be guided to the body under increased pressure, for example under a pressure of 2 bar or higher. In other exemplary embodiments, in the first step 2 the component can also be zonally or entirely heated using a gas burner and subsequently cooled using an air jet in the second step 3.

[0043] If the ceramic component is guided using a conveyor to the liquid as quenchant, the components can be allowed to fall into the liquid in order to achieve the thermal shock treatment. Here the liquid has the second temperature. Alternatively the component can also be plunged into the liquid.

[0044] In some exemplary embodiments the temperature change to the first and the second temperature can be carried out in a single device, for example, when a gas is worked with for a quenching from a first temperature. For this purpose a combined heating- and quenching-system can be used. One example therefor is the heating in a vacuum hardening unit, wherein the heating can be performed with or without vacuum, possibly a heating with subsequent high-pressure-gas quenching.

[0045] In some exemplary embodiments an inhomogeneous temperature field on or in the component can be set during the temperature change process. In some exemplary embodiments a rapid heating of the component in combination with a rapid cooling can thereby be achieved. The thermal shock treatment can pertain to a near-surface zone of the component or the entire component. It is also possible here that the thermal shock treatment is carried out in a region wherein a maximum stress of the component occurs in use. Under certain circumstances edges of a body can also be subjected to the thermal shock treatment.

[0046] FIGS. 2a and 2b show schematic depictions of components 5 and 6 that are tested using the method 1. The component 5 is a cylindrical roller, and the component 6 a ball. The components 5 and 6 can, for example, serve as rolling elements. The components 5 and 6 include as ceramic material at least one of the materials Si.sub.3N.sub.4, SiAlON, SiC, Al.sub.2O.sub.3, ZrO.sub.2, ZTA, or ATZ.

[0047] However, all possible other, for example, ceramic, components can be tested using the method 1. These can be, for example, components that are installed in rolling-element-, roller-, or sliding-applications. For this purpose the components are subjected as described to a test using thermal shock and subsequently impinged, for example, with crack-penetrating dye, in order to detect supercritically long cracks and thus to be able to eliminate components that are damaged or not suitable for use.

[0048] The exemplary embodiments and their individual features disclosed in the above description, the following claims, and the accompanying Figures can be meaningful and implemented both individually and in any combination for the realization of an exemplary embodiment in its various designs. In some further exemplary embodiments, features that are disclosed in other exemplary embodiments as device features can also be implemented as method features. Furthermore, features that are implemented in some exemplary embodiments as method features can also optionally be implemented in other exemplary embodiments as device features.

[0049] Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved an improved method of testing a ceramic component.

[0050] Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

[0051] All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

REFERENCE NUMBER LIST

[0052] 1 Method

[0053] 2 Heating or cooling

[0054] 3 Heating or cooling

[0055] 4 Testing

[0056] 5 Component

[0057] 6 Component