EP3120036A1

EP3120036A1 - Bearing element for a sliding or rolling bearing

Info

Publication number: EP3120036A1
Application number: EP15714171.4A
Authority: EP
Inventors: Christian SCHULTE-NÖLLE; Claus Müller; Rudnik YEGOR
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2014-03-20
Filing date: 2015-03-03
Publication date: 2017-01-25
Also published as: WO2015139699A1; KR20160134734A; DE102014205164B4; JP2017514022A; CN106415036A; US20170138401A1; DE102014205164A1

Abstract

The invention relates to a bearing element (1) for a sliding or rolling bearing, said bearing element (1) being made of, at least in sections, powder metallurgical composite material which contains a metallic binding phase and a hard phase, or comprises one composite material of said type. The metallic binding phase is based on at least one element from the group: chromium, cobalt, molybdenum, nickel, titanium.

Description

Name of the invention

Bearing element for a plain or roller bearing

description

FIELD OF THE INVENTION The invention relates to a bearing element for a sliding or roller bearing, which bearing element is formed at least in sections from a powder metallurgical composite material which contains a metallic binder phase and a hard material phase, or comprises such a composite material. Background of the invention

Bearing elements for sliding or roller bearings, in particular in the form of bearing rings are well known and are usually made of mechanically particularly durable materials, d. H. in particular classical Wälzlagerstäh- len, formed. For corrosive particularly demanding applications are also powder metallurgical composite materials and plastic and ceramic materials for the formation of corresponding bearing elements known.

In particular with regard to the use of corresponding bearing elements in non-conventionally lubricated operating situations, ie primarily in corrosive (thin) liquid, in particular aqueous, media in which corresponding bearing elements permanently outsourced and from which the bearing elements are flushed, there is a need for development of mechanical as well corrosive highly stressable materials to form corresponding bearing elements. Such, in particular due to a not effectively realizable lubrication of the bearing elements, mechanically as well as corrosive highly demanding operating situations are particularly in applications in hydraulic structures, such. Marine power plants, locks or in salt or fresh water turbines, or in drill head, compressor or pump bearings. In these applications, there is also the risk of cavitation. Summary of the invention

The invention has for its object to provide a, in particular mechanically as well as corrosive, highly stressed bearing element. The object is achieved by a bearing element of the type mentioned, which is characterized in that the metallic binder phase is based on at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium. According to the invention, a bearing element is proposed for a sliding or roller bearing, which bearing element is at least partially formed or made from a powder metallurgical composite material containing a metallic binder phase and a hard material phase, or at least partially comprises such a powder metallurgical composite material. The special feature of the bearing element according to the invention lies in particular in the (chemical) composition of the metallic binder phase.

According to the invention, the metallic binder phase is based on at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium. By this is meant that the metallic binder phase is formed from at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium or at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium as the main constituent. However, this also means that the metallic binder phase is formed from or comprises at least one metallic compound containing chromium and / or cobalt and / or molybdenum and / or nickel and / or titanium. The elements mentioned can therefore be elemental or (chemically) bound. The powder metallurgical composite material is generally characterized by a comparatively tough metallic binder phase and a comparatively hard hard material phase. The toughness of the metallic binder phase compensates for the brittleness of the hard material phase and leads to a sufficient (total) impact strength of the composite material. The hardness of the hard material phase gives the composite a high hardness. Both the metallic binder phase and the hard material phase are extremely resistant to corrosion. The powder metallurgical composite material therefore has a high strength, toughness, hardness, rollover and wear resistance, in particular to abrasion, adhesion and cavitation, and a high corrosion resistance. The same applies to the bearing element made or produced according to this invention.

The comparatively high toughness of the composite material makes it possible, even mechanically as well as corrosive high-loadable larger bearing elements, d. H. especially larger bearing rings, namely bearing rings up to a diameter of up to about 1000 mm to realize. Related to use in a sliding or rolling bearing, the toughness of the composite reduces equally the formation of viable cracks due to the overrolling of foreign particles and the possibility of high dynamic stress failure.

Depending on the specific chemical and proportionate composition of the composite material, bearing elements with the following physical or mechanical characteristics can be realized in particular: density 5 - 15 g / cm ³ , compressive strength 2000 - 8000 MPa, modulus of elasticity 400 - 700 GPa, hardness 1000 - 2000 HV. The numerical values mentioned are purely exemplary and may, as mentioned, vary depending on the respective chemical as well as proportionate composition of the composite material, ie in particular also be higher or lower.

The special chemical as well as proportionate composition of the powder metallurgical composite material is thus the basis for the special Property profile of the bearing element according to the invention, which predestines the bearing element, in particular also without conventional lubrication, for use in areas of mechanical and corrosive stress. Corresponding applications can z. B. in corrosive environments, ie, for example, in non-aqueous or aqueous, especially chlorine-containing, and acidic or basic environments such. As in the field of tidal or marine power plants, ie in particular offshore wind turbines, offshore conveyors, generally hydraulic structures, or other marine applications such. As ships, ie in particular marine propulsion, or in the range of pumps and compressors. Even dry running applications or minimally lubricated application areas are relevant, eg. B. in the field of food and pharmaceutical technology.

The bearing element according to the invention or the composite material forming this is known by powder metallurgical processes, d. H. based on a powdered starting material or a powdery starting material mixture prepared. The use of powder metallurgical methods is particularly advantageous because it allows the formation of microstructures with (nearly) isotropic properties. Likewise, the use of powder metallurgical methods generally permits a near net shape production or primary shaping of the bearing element, which reduces the need for mechanical, ie. H. In particular cutting, post-processing steps largely reduced and therefore advantageous in manufacturing technology and thus also economically.

Such a powder metallurgical process for producing the bearing element may be, for example, hot isostatic pressing, HIP for short; Consequently, it is a powder metallurgical production technology principle from the field of primary shaping, according to which a powdered starting material or a pulverulent starting material mixture is compacted or pressed and sintered under pressure and temperature. Another conceivable powder metallurgical method for producing a bearing element according to the invention is the spray compacting method, which is also a powder metallurgical production engineering principle in the field of primary shaping, according to which a pulverulent starting material or a pulverulent starting material mixture is sprayed onto a carrier material and layered An advantage of the spray-compacting process over other powder-metallurgical processes is that it does not necessarily require complete compaction of the powdery starting materials Composite material, which can be formed with spatially or spatially distributed substance or concentration gradient ,

In the context of powder metallurgical production of the composite material, it is conceivable to combine the pulverulent material or material mixture forming the metallic binder phase with a pulverulent material or material mixture forming the hard material phase in a powder metallurgical process. Alternatively, it is conceivable first to produce the metallic binder phase via a powder metallurgical process and to form the hard material phase in the metallic binder phase by the subsequent targeted formation of precipitates, for example in the course of the primary shaping of the composite material or a heat treatment.

The metallic binder phase may additionally contain fractions of iron and / or carbon and / or nitrogen and / or at least one iron and / or carbon and / or nitrogen-containing compound. In this way, the property spectrum of the metallic binder phase can be specifically influenced with regard to a specific field of application of the bearing element according to the invention. Likewise, if appropriate, the connection between the metallic binder phase and the hard material phase, which is typically formed from individual hard material phase grains, can also be improved in this way. As mentioned above, the metallic binder phase may also be formed from or comprise at least one metallic compound containing chromium and / or molybdenum and / or nickel and / or cobalt and / or titanium. So it is so z. B. possible that the elements chromium, molybdenum, titanium, if present, are present in bonded form and therefore with other constituents of the metallic binder phase, such as. As iron and / or carbon and / or nitrogen are chemically bonded. It is thus conceivable, for example, for the metallic binder phase to contain as the carbon-containing compound chromium and / or molybdenum and / or titanium carbide.

The hard material phase associated with the powder metallurgical composite material can be formed from at least one of the following hard material compounds or comprise at least one of the following hard material compounds: borides, carbides, in particular titanium carbide and / or tungsten carbide, carbonitrides, in particular titanium carbonitride, nitrides, in particular titanium nitride, silicides. The hard material phase can therefore particularly hard metals, ie in particular sintered carbide carbides such. As tungsten carbide, and / or cermets, ie in a metallic matrix, for. B. based on nickel and / or molybdenum, contained ceramic particles such. As titanium carbide, titanium carbonitride or titanium nitride particles, be formed or include such. Of course, mixtures (chemically) of different hard material compounds are conceivable. The hard material phase can also positively influence the thermal conductivity of the composite material, which is advantageous in particular with regard to the possibility of heat removal from the bearing element according to the invention and thus the cooling capacity of the bearing element according to the invention. This applies in particular to the use of carbides based on carbides, in particular tungsten carbides, whose thermal conductivity is many times higher than the thermal conductivity of unalloyed or stainless steels which are typically used to form conventional bearing elements. As mentioned, the hard material phase is typically formed of or comprises individual hard material phase grains. The powder metallurgical composite material may also contain an intermediate phase, which is formed around the hard material phase grains and via which a bonding of the hard material phase grains to the metallic binder phase is realized. For the example of hard cermets formed from cermets, ie in particular titanium carbonitride or titanium carbide, a κ-phase, ie a complex carbide structure was detected, which lays around the hard material phase grains and ensures a firm connection of these to the metallic binder phase.

The volume fraction of the hard material phase in the powder metallurgical composite material is in particular in a range between 50 and 99% by volume, preferably in a range between 85 and 95% by volume. Accordingly, the volume fraction of the metallic binder phase in the powder metallurgical composite material is in particular in a range between 1 and 50% by volume, preferably in a range between 15 and 5% by volume. It must be ensured that the volume fraction of the hard material phase does not fall below 50% by volume in order to ensure a high hardness of the composite material and, consequently, of the bearing element. Nevertheless, in exceptional cases, the volume fraction of the hard material phase may also be below 50% by volume or, in exceptional cases, the proportion of the metallic binder phase may also be above 50% by volume.

The hardness of the bearing element is at least in the region of its surface or boundary layer or in near-surface or near-edge regions, in particular between 1000-2000 HV (Vickers hardness), typically above 1100 HV. The surface or boundary layer of the bearing element can have a certain structural area, which differs from further internal structural areas in its properties, ie in particular the hardness, and can therefore be delimited from further internal structural areas. Such surface or boundary layer areas are typically sliding or rolling surfaces provided on the bearing element side, ie in particular raceway surfaces for sliding or rolling bodies or corresponding sliding surfaces. or rolling elements surfaces. Of course, the bearing element can also have a consistent overall hardness. In exceptional cases, the hardness of the bearing element, possibly even in sections, below 1000 HV or above 2000 HV.

For the property profile of the composite material, besides the chemical and the proportionate composition, i. H. the volume-wise proportion of the metallic binder phase and the hard material phase, in particular also the shape, size and distribution of the hard material phase forming hard material phase grains in the serving as a matrix metallic binder phase of importance. The hard-phase grains may generally be of coarse to fine grained. The hard material phase grains are preferably round or round shape. In the context of the production of the composite material should on a coherent as possible distribution of the hard material phase forming. Hard material phase grains are taken in the serving as a matrix metallic binder phase.

A characteristic of the shape, size and distribution of the hard material phase forming hard material phase grains is the surface quality and thus the roughness of the bearing element in a finished state, ie after finishing, represents. Basically, in connection with the roughness of corresponding bearing elements that larger outer diameter of Have bearing elements in technical-economic terms higher roughness of the bearing elements. Investigations of the roughness showed that for bearing elements with outer diameters above about 200 mm mean roughness R _a in the range 0.1 - 1. 0 μιτι and for bearing elements with outer diameters below about 200 mm mean roughness R _a in the range of 0.02 - 0.2 μιτι be realized, which is due to a coherent and homogeneous microstructure, ie a particularly coherent and homogeneous distribution of the hard material phase grains in the metallic binder phase, in particular in combination with a suitable manufacturing technology.

In the bearing element according to the invention, it may be, for. B. a bearing ring, ie an outer or an inner ring, a sliding or rolling bearing act. The bearing element may also be a sliding or rolling element or a rolling element cage for receiving rolling elements.

The invention further relates to a bearing, d. H. a sliding or rolling bearing, which comprises at least one as described above, inventive bearing element. As mentioned, the bearing element (s) may be, in particular, bearing rings and / or sliding or rolling elements and / or a rolling element cage for accommodating rolling elements. With regard to the bearing according to the invention, all statements relating to the bearing element according to the invention apply analogously.

Short description of the drawing

An embodiment of the invention is illustrated in the drawing and will be described in more detail below. Show it:

Figure 1 is a schematic diagram of a rolling bearing comprising a bearing element according to an embodiment of the invention, Figure 2 shows a detail of a microstructure of a powder metallurgical composite material for forming a bearing element according to an embodiment of the invention, and

FIG. 3 shows a diagram for illustrating the corrosion resistance of a bearing element according to the invention in comparison to a bearing element formed from a conventional corrosion-resistant bearing steel.

Detailed description of the drawing

Figure 1 shows a schematic diagram of a bearing element 1 according to an embodiment of the invention. The bearing element 1 is part of a roller bearing 2. The bearing element 1 is the outer ring 3 of the rolling bearing. gers 2. The inner ring 4 of the rolling bearing 2 could equally be formed as a corresponding bearing element 1 according to an embodiment of the invention. The same applies to the rolling elements 5 rolling between the outer ring 3 and the inner ring 4 as well as to the rolling element cage 6 receiving or guiding the rolling elements 5.

The bearing element 1 could also be corresponding components of a plain bearing. The bearing element 1 is made of a powder metallurgical, d. H. powder metallurgically produced, composite material formed. The powder metallurgical composite material comprises a metallic binder phase and a hard material phase formed from at least one hard material. The powder metallurgical composite material may accordingly be referred to as "metal matrix composite".

The metallic binder phase is generally based on at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium. By this is meant that the metallic binder phase is formed from at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium or at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium as the main constituent. This is to be understood as meaning that the metallic binder phase is formed from or comprises at least one metallic compound containing chromium and / or cobalt and / or molybdenum and / or nickel and / or titanium. The said elements can therefore be present elementary or (chemically) bound.

The metallic binder phase may additionally contain fractions of iron and / or carbon and / or nitrogen and / or at least one iron and / or carbon and / or nitrogen-containing compound. Chromium and / or molybdenum and / or titanium carbide is particularly suitable as the carbon-containing compound. The hard material phase is generally formed from at least one of the following hard material compounds or comprises at least one of the following hard material compounds: borides, carbides, in particular titanium carbide and / or tungsten carbide, carbonitrides, in particular titanium carbonitride, nitrides, in particular titanium nitride, silicides. The hard material phase is typically present in the form of single or multiple bonded hard material phase grains. The hard material phase grains typically have a particle size of about 0.5 to 10 μιτι, in particular 0.9 to 6 μιτι on. The structure of the composite material therefore consists in particular of individual or several interconnected hard material phase grains, which are surrounded by the metallic binder phase. The metallic binding phase thus extends between the hard material phases and binds them in the structure. The microstructure of the composite material can be compared with a masonry comprising several bricks connected by a mortar, the hard material phases representing the bricks and the metallic binder phase representing the mortar.

The hard material phase has a proportion of 50 to 99% by volume, in particular a proportion of between 85 and 95% by volume, in the composite material. The metallic binder phase has a proportion of 1-50% by volume, in particular a proportion of between 15 and 5% by volume.

In a specific embodiment, the composite material may contain nickel and bound chromium as a metallic binder phase. The hard material phase consists in this specific embodiment of tungsten carbide. The proportion of hard material phase is between 85 and 95 vol .-%. The high content of the hard material phase ensures a very high hardness, typically 1 150 - 1750 HV1, of the composite material and thus of the bearing element 1. The toughness of the metallic binder phase compensates for the brittleness of the hard material phase and ensures good impact resistance, typically K _c 7 - 19

MN / mm, of the composite material and thus of the bearing element 1. The compressive strength of the composite material and thus of the bearing element 1 lies between 3500 and 6300 MPa, the modulus of elasticity lies in a range between 500 and 650 GPa, the Poisson number is between 0.21 and 0.22 and the density between in a range of 13.0 and 15.0 g / cm ³ . The grain size of the hard material phase grains is between 0.5 and 5 μιτι.

Similar properties can be achieved in a further concrete embodiment of the composite material, which differs from the above concrete embodiment essentially in that the metallic binder phase consists of cobalt as the main component.

In a further concrete embodiment of the composite material, this may contain, as the metallic binder phase, mainly nickel and cobalt. The metallic binder phase here additionally contains carbon or carbide compounds, in particular nickel carbide or cobalt carbide compounds. The hard material phase is formed here from titanium carbide or titanium carbonitride. In the composite material grains here an intermediate phase is formed around the hard material phase, via which a firm connection of the hard material phase grains is realized to the metallic binder phase. The intermediate phase is a so-called κ phase, ie a complex carbide structure. The hardness of the composite material and thus of the bearing element 1 is between 1 100 and 1650 HV, the impact strength is about K _1c 8 - 14 MN / mm ³ ' ² , the modulus of elasticity is between 370 and 450 GPa, the density is between 5.8 and 6.9 g / cm ³ . It should be emphasized that the comparatively low density of the composite material leads to a comparatively low component weight.

FIG. 2 shows a detail of a microstructure of a powder metallurgical composite material similar to the exemplary embodiment described above for forming a bearing element 1 according to one exemplary embodiment of the invention. The metallic binder phase containing mainly nickel and molybdenum here is indicated by reference numeral 7, the hard material phase grains consisting of titanium carbonitride hereby referenced 8, and the κ phase by reference numeral 9. The connection of the hard material phase Countersurfers 8 to the metallic binding phase 7 takes place via the intermediate phase 9 immediately surrounding the hard-material phase grains 8.

With all embodiments of the composite material, depending on the outside diameter, bearing elements 1 with mean roughness values R _{a are} interposed

0.02 and 1, 0 μιτι feasible, which means a coherent and homogeneous distribution of the hard material phase grains in the metallic binder phase and, in particular due to the selection of suitable manufacturing parameters, a high surface quality of the bearing elements 1.

Overall, the bearing element 1 forming composite material and thus also the bearing element 1 characterized by a high strength, high toughness, high hardness, high rollover and wear resistance, high thermal conductivity and high corrosion resistance.

FIG. 3 shows a diagram for illustrating the corrosion resistance of a bearing element 1 according to the invention in comparison to a bearing element formed from a conventional corrosion-resistant bearing steel. The corrosion resistance of the composite material forming the bearing element 1 according to the invention can be illustrated with reference to FIG. 3 in comparison to a corrosion resistance improved from a conventional rolling bearing steel.

In the diagram shown in FIG. 3, the electrical current (y-axis) is plotted against the electrical potential (x-axis). Shown are test results from electrochemical investigations of the pitting corrosion potential or the repassivation potential (Ag / AgCl, 3.5% NaCl, 20 ° C.). The curve 10 represents the measurement results for a bearing element according to the invention

1, the curve 1 1 represents the measurement results for a non-inventive bearing element formed from a conventional bearing steel.

As can be seen, the material dissolution indexed by the rise of the curve 10 starts significantly later in the bearing element 1 according to the invention than in the bearing element not according to the invention. The repatriation potential, ie the potential at which the curves hit the x-axis again after the rise is significantly higher in the case of the bearing element 1 according to the invention compared to the bearing element not according to the invention. The investigations prove the very good corrosion resistance of the bearing element 1 according to the invention.

LIST OF REFERENCE NUMBERS

bearing element

2 rolling bearings

3 outer ring

4 inner ring

5 rolling elements

6 rolling element cage

7 Metallic binder phase containing nickel and molybdenum 8 Hard material phase grains

9 κ phase

10 curve

1 1 curve

Claims

claims

1 . Bearing element (1) for a sliding or roller bearing, which bearing element (1) is at least partially formed of a powder metallurgical composite material which contains a metallic binder phase and a hard material phase, or comprises such a composite material, characterized in that the metallic binder phase at least at least one element of the group: chromium, cobalt, molybdenum, nickel, titanium.

2. Bearing element according to claim 1, characterized in that the metallic binder phase additionally contains fractions of iron and / or carbon and / or nitrogen and / or at least one iron and / or carbon and / or nitrogen-containing compound.

3. Bearing element according to claim 2, characterized in that the metallic binder phase contains as carbon-containing compound chromium and / or molybdenum and / or titanium carbide.

4. Bearing element according to one of the preceding claims, characterized in that the hard material phase consists of individual hard material grains or comprises grains and the composite material contains an intermediate phase, which is formed around the hard material phases grains and via which a connection of the hard material phase grains to the metallic binder phase is realized.

5. Bearing element according to one of the preceding claims, characterized in that the hard material phase is formed from at least one of the following hard compounds or at least one of the following hard material compounds comprises: borides, carbides, in particular titanium carbide and / or tungsten carbide, carbonitrides, in particular Titanium carbonitride, nitrides, in particular titanium nitride, silicides.

6. Bearing element according to one of the preceding claims, characterized in that the hard material phase in the composite material, a proportion of 50 to 99 vol .-%, in particular a proportion between 85 and

95% by volume, and the metallic binder phase has a proportion of 1-50% by volume, in particular a proportion of between 15 and 5% by volume.

7. Bearing element according to one of the preceding claims, characterized in that it, at least in the region of the surface, in particular in the region of sliding or rolling surfaces, a hardness of 1000 - 2000 HV, in particular above 1 100 HV.

8. Bearing element according to one of the preceding claims, characterized in that it has an average roughness value R _a between

0.02 and 1, 0 μιτι has.

9. Bearing element according to one of the preceding claims, characterized in that there is a bearing ring (3, 4) or a sliding or rolling body (5) or a Wälzkörperkäfig (6) for receiving rolling elements

(5).

10. Bearing, in particular sliding or rolling bearing, comprising at least one bearing element (1) according to one of the preceding claims.