CHAIN ELEMENT AND METHOD FOR THE PRODUCTION THEREOF

Abstract

A chain element (2), in particular a chain pin (4), for joining at least two chain links (3), characterized in that it comprises a surface layer (5) containing boron and vanadium, formed by at least one step of diffusing boron and vanadium in the areas of the chain element (2) which are close to the surface. The surface layer (5) containing boron and vanadium is formed by boriding and subsequently vanadizing a substrate material having a carbon content of 0.60 wt.-% to 1.0 wt.-%.

Claims

1. A chain element, comprising a surface layer that contains boron and vanadium and is formed by diffusion of boron and vanadium into areas of the chain element that are close to a surface thereof, the surface layer containing the boron and the vanadium is formed by a boriding process and a subsequent vanadizing process, wherein the surface layer containing the boron and the vanadium is divided into at least first and second surface layer sections, the first surface layer section is directly adjacent to a substrate material of the chain element and consists essentially of boron vanadium compounds, the substrate material of the chain element has a carbon content of 0.60 wt. % to 1.0 wt. %, and the second surface layer section is adjacent to the first surface layer section and consists essentially of substoichiometric crystalline vanadium carbide VC.sub.1-x, wherein x=0.65 to 0.9, and wherein any carbon within the vanadium carbide is derived from the carbon content of the substrate material.

2. The chain element according to claim 1, wherein the surface layer containing the boron and the vanadium has a hardness of 2000-3500 HV.

3. The chain element according to claim 1, wherein the surface layer containing the boron and the vanadium has a layer thickness from 10 to 350 m.

4. The chain element according to claim 1, wherein the second surface layer has a layer thickness from 9 to 16 m.

5. The chain element according to claim 1, wherein the surface layer contains a maximum boron concentration of 1 at-%.

6. The chain element according to claim 1, wherein the surface layer contains alumina particles having a maximum particle size of 10 m being present in a maximum concentration of 1 at-%.

7. A chain pin for connecting at least two chain links of a chain, said chain pin comprises a surface layer that contains boron and vanadium and is formed by diffusion of the boron and the vanadium into areas of the chain pin that are close to a surface thereof, the surface layer containing the boron and the vanadium is formed by a boriding process and a subsequent vanadizing process, wherein the surface layer containing the boron and the vanadium is divided into at least first and second surface layer sections, the first surface layer section is directly adjacent to a substrate material of the chain pin, the substrate material of the chain pin has a carbon content of 0.60 wt. % to 1.0 wt. %, and the second surface layer section that is adjacent to the first surface layer section consists essentially of substoichiometric crystalline vanadium carbide wherein x=0.65 to 0.9, and wherein any carbon within the vanadium carbide is derived from the carbon content of the substrate material.

8. The chain pin according to claim 7, wherein the surface layer containing the boron and the vanadium has a hardness of 2000-3500 HV.

9. The chain pin according to claim 7, wherein the surface layer containing the boron and the vanadium has a layer thickness from 10 to 350 m.

10. The chain pin according to claim 7, wherein the second surface layer has a layer thickness from 9 to 16 m.

11. The chain pin according to claim 7, wherein the surface layer contains a maximum boron concentration of 1 at-%.

12. The chain pin according to claim 1, wherein the surface layer contains alumina particles having a maximum particle size of 10 m being present in a maximum concentration of 1 at-%.

13. A method for the production of a chain element, with a surface layer containing boron and vanadium, comprising the steps: preparing the chain element, diffusing boron and vanadium into areas of the chain element that are close to a surface thereof for construction of the surface layer containing the boron and the vanadium, performing a thermochemical boriding process and a subsequent thermochemical vanadizing process of the chain element, such that the surface layer containing the boron and the vanadium is divided into at least first and second surface layer sections, the first surface layer section is directly adjacent to a substrate material of the chain element and consists essentially of boron vanadium compounds, the substrate material of the chain pin has a carbon content of 0.60 wt. % to 1.0 wt. %, and the second surface layer section that is adjacent to the first surface layer section consists essentially of substoichiometric crystalline vanadium carbide VC.sub.1-x, wherein x=0.65 to 0.9, and wherein any carbon within the vanadium carbide is derived from the carbon content of the substrate material.

14. The method according to claim 13, further comprising performing the thermochemical treatment in a temperature range from 800 to 1200 C.

15. The method according to claim 13, further comprising performing the thermochemical treatment for a duration of 2 to 24 hours.

16. The method according to claims 13, wherein the measure for the construction of the surface layer containing boron and vanadium is performed such that the surface layer containing boron and vanadium is constructed with a layer thickness of 10 to 350 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] One embodiment of the invention is shown in the drawing and will be described in more detail below. Shown are:

[0033] FIG. 1 shows a characteristic section of a chain comprising multiple chain elements,

[0034] FIG. 2 shows a chain element in the form of a chain pin for connecting at least two chain links of a chain,

[0035] FIG. 3 shows an enlargement of the surface layer containing boron and vanadium shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] FIG. 1 shows a characteristic section of a chain 1 comprising multiple chain elements 2. The chain 1 can be constructed as a toothed chain and used, for example, for transmitting force in the drive train or as part of the drive train of a motor vehicle.

[0037] Clearly the chain 1 comprises multiple chain elements 2 in the form of chain links 3, in particular, clip-shaped links, which are arranged one after the other and are connected to each other by chain pins 4. FIG. 2 shows a separate representation of a chain element 2 in the form of a chain pin 4 for connecting at least two chain links 3 of a chain 1.

[0038] The chain elements 2 forming the chain 1, that is, the chain links 3 and the chain pins 4, are formed from a metallic substrate material 8, in particular, a steel having a carbon content of 0.6 wt. % to 0.8 wt. %, e.g. CK75 or 100Cr6. The surface of the chain elements 2 or a part of the chain elements 2 has been subjected to a thermochemical surface treatment in the form of forming a surface layer 5 containing boron and vanadium.

[0039] Specifically, the chain elements 2 are first subjected to boron diffusion by means of boriding and then to vanadium diffusion by means of vanadizing. After the boriding, a surface layer containing boron or boron compounds is formed, from which a surface layer is formed that contains boron and vanadium, that is, in particular, boron vanadium compounds, such as VB and/or V.sub.2B, due to the vanadizing and the associated diffusion of vanadium.

[0040] As can be seen in FIG. 3, the surface layer 5 containing boron and vanadium can have a surface layer section 6 that contains essentially substoichiometric vanadium carbide and is formed by the vanadizing process, wherein this surface layer section 6 is formed on the surface layer section 7 containing boron and vanadium, that is, essentially boron vanadium compounds. Both surface layer sections 6, 7 are part of the surface layer 5 containing boron and vanadium.

[0041] In one embodiment, the metallic substrate material 8 has a carbon content of 0.6 wt. % to 1.0 wt. %. Due to this relatively high level of carbon, the metallic substrate material 8 promotes diffusion of carbon into both surface layer sections 6, 7 during the boriding and vanadizing steps. The diffusion of carbon into the surface layers sections 6, 7 improves the mechanical strength of the surface layers 5. The high carbon content of the metallic substrate material 8 also results in vanadium carbide being formed in the surface layer 5 after the boriding and vanadizing steps.

[0042] A micro hardness of the vanadium carbide depends on the carbon content of the substrate material. For a steel substrate material 8, increasing the steel carbon content results in an increase of the thickness and micro hardness of the surface layer 5. By increasing the steel carbon content, the homogeneity of the substoichiometric vanadium carbide VC.sub.1-x increases. The wear performance of the surface layer 5 increases with increasing the micro hardness and homogeneity of the substoichiometric vanadium carbide VC.sub.1-x (x=0.65-0.9). The most preferable carbon content of the substrate material 8 for this process is in the range of 0.6 wt.-% to 0.8 wt.-%.

[0043] The surface layer 5 containing boron and vanadium has a layer thickness of approx. 250 m. This thickness can be divided approx. 100 m to the surface layer section 6 containing essentially vanadium and approx. 150 m to the surface layer section 7 containing essentially boron and vanadium, that is, essentially boron vanadium compounds.

[0044] The surface layer 5 containing boron and vanadium imparts an improved characteristics profile to the chain element 2, wherein, in particular, the wear resistance and the corrosion resistance are improved due to the high hardness in the range of approx. 3000 HV (Vickers hardness) of the surface layer 5 containing boron and vanadium, along with sufficient ductility.

[0045] The production of a chain element 2, in particular, a chain pin 4 for connecting at least two chain links 3, with a surface layer 5 containing boron and vanadium, is performed by means of a method with the steps of preparation of the chain element 2 and the diffusion of boron and vanadium into areas of the chain element 2 that are close to the surface for forming the surface layer 5 containing boron and vanadium.

[0046] As a measure for the diffusion of boron and vanadium into areas of the chain element 2 that are close to the surface, preferably a thermochemical boriding process and a thermochemical vanadizing process subsequent to this boriding process are performed on the chain element 2.

[0047] The thermochemical boriding and also the thermochemical vanadizing of the chain element 2 are performed, e.g., at temperatures in the range from approx. 900 C. for a duration of approx. 4 hours, so that a homogeneous surface layer 5 containing boron and vanadium is formed with the specified layer thickness of approx. 250 m.

LIST OF REFERENCE NUMBERS

[0048] 1 Chain

[0049] 2 Chain element

[0050] 3 Chain link

[0051] 4 Chain pin

[0052] 5 Surface layer

[0053] 6 Surface layer section

[0054] 7 Surface layer section

[0055] 8 Substrate material