EP1974072A1

EP1974072A1 - Method of coating a cemented carbide or cermet substrate body and coated cemented carbide or cermet body

Info

Publication number: EP1974072A1
Application number: EP06805498A
Authority: EP
Inventors: Hartmut Westphal; Hendrikus Van Den Berg
Original assignee: Kennametal Widia Produktions GmbH and Co KG
Current assignee: Kennametal Widia Produktions GmbH and Co KG
Priority date: 2006-01-17
Filing date: 2006-11-07
Publication date: 2008-10-01
Also published as: RU2008128431A; DE102006002371A1; CN101310035A; WO2007082498A1; US20100151260A1; CA2635020A1; JP2009523618A; KR20080085876A; BRPI0621001A2

Abstract

The invention relates to a method of coating a cemented carbide or cermet substrate body by means of PVD, in which the fully sintered substrate body is subjected without further intermediate treatment before PVD coating to a blasting treatment using a particulate blasting agent until the zone close to the surface of the substrate body has a residual stress which is at least essentially of the same magnitude as the residual stress present in the single or first applied PVD layer. The invention further relates to such a coated cemented carbide or cermet body, in particular in the form of a cutting tool.

Description

Process for coating a hard metal or Cernnet substrate body and coated hard metal or cermet body

The invention relates to a method for coating a cemented carbide or cermet substrate body by means of physical vapor deposition (PVD).

The invention further relates to a coated hard metal or cermet body.

Carbide or cermet bodies in various compositions have been suggested for many applications. Here, the substrate body composition is adapted to the application, for example, a high hardness, thermal shock resistance or wear resistance, the latter in particular in tools for machining operations in the foreground. In certain cases, coated substrate body have proven their coating consisted of one or more layers. Coating materials are carbides, nitrides, carbonitrides, oxicarbonitrides, oxynitrides or oxides of the metals of the IVa to VIa group of the periodic table or aluminum compounds such as Al ₂ O ₃ and TiAIN. In particular, physical or chemical vapor deposition processes are used for coating substrate bodies. As a rule, physical deposition methods (PVD methods) have the advantage that the coating can be applied at lower temperatures. According to the state of the art, the substrate bodies are ground before the PVD coating. Unpolished substrate surfaces (ie in the sintered state) left substrates have virtually no compressive or tensile residual stresses. Due to the grinding process, residual compressive stresses are generated in the surface of the substrate body which can be between -200 and -1200 MPa for carbide. PVD layers always have residual compressive stresses of about -1800 to -4000 MPa due to the way in which the layer-forming constituents (ions) are incorporated into the layer with high energy. Thereafter, the difference in residual compressive stresses between the coating and substrate for ground substrates is smaller than for substrates left in the sintered state. The difference in the residual stresses between the substrate body and the coating causes shear stresses which adversely affect the layer adhesion. For this reason, PVD-coated substrates that are not ground show poorer machining performance.

It is an object of the present invention to improve the service life of PVD-coated substrate bodies.

To solve this problem, a method according to claim 1 or the substrate body is proposed according to claim 9.

Further developments of the inventions are described in subclaims 2 to 8 and 10.

The core idea of the present invention is that the finished sintered substrate body made of a hard metal or a cermet without further intermediate treatment before the PVD coating of a blasting using a granular blasting agent is subjected until the near-surface zone of the substrate body has a residual stress, the at least substantially equal to the residual stress present in the single or first applied PVD layer.

Surprisingly, it has been found that an approximation of the residual stress of the substrate body in the substrate body surface near zones to the known compressive residual stress of a PVD layer causes a significant improvement in tool life. With the jet method known in principle, the near-surface zones are compacted, which is accompanied by a pressure surge. By approximation of this compressive residual stress to the known compressive residual stress of the first applied or single applied PVD layer, the cutting performance could be improved.

Preferably, a blasting agent is used with particles having particles with a maximum diameter of 600 microns, preferably at most 150 microns and in particular between 15 and 100 microns. The substrate body, which is treated according to a development of the invention in the dry-jet method, is preferably irradiated with at least substantially spherical blasting agents or blasting agents which have a round grain shape. Suitable blasting agents are, in particular, pressure-blasted blasting, cast iron granules, heavy metal powder or alloys, glass, corundum, hard metal granules and / or unbreakable ceramics made therefrom.

Further preferably, the steel or the means are directed by compressed air under a pressure of at least 1, 0 x10 ⁵ - 10 x10 ⁵ Pa, preferably 1, 5 x10 ⁵ -3.5 x10 ⁵ Pa on the substrate body.

Particularly advantageous is the irradiation of the substrate body with directed perpendicular to the surface of abrasive particles.

The blast treatment of the type described above has proven particularly in connection with a subsequent PVD coating consisting of carbides, nitrides, carbonitrides, oxides or oxicarbonitrides of the elements of the IVa to Vla group of the Periodic Table or of Al ₂ O ₃ , AITiN or AIN existed. The thickness of the individual layers was preferably between 0.1 μm and 10 μm with a total thickness (in the case of multilayer coatings) of not more than 20 μm.

In a corresponding manner, the object is achieved by the coated hard metal or cermet body according to claim 9, apply to the corresponding advantages as described above. Such a coated hard metal or cermet body is designed in particular as a cutting tool for drilling, milling or turning.

In one specific embodiment, indexable inserts have been coated with an AlTiN coating applied by PVD at 350 ° to 600 ° (coating temperature). While the tools that were coated after sintering without further treatment or only after a grinding treatment, had to be replaced after a relatively short time due to wear, the service life of corresponding tools of the same configuration, after sintering a method of the invention, namely a blast treatment between 10 and 60 seconds have been significantly improved. This is because the PVD layers, the residual compressive stresses measured by the SIN ² -ψ process, were on the order of -1.5 to -3.5GPa, which had residual tensile stresses or very small compressive residual stress in the surface near edge zones of the substrate body of a maximum of 100 MPa opposed. If, on the other hand, the compressive stress of the near-surface zone of the substrate body is increased to the compressive residual stress dependent on the coating material and the PVD parameters (except for +/- 10%) by the jet treatment, in particular in the dry-jet method with round grains of 50 μm and 100 μm, this increase results the compressive residual stress to much better wear resistance of the tools.

Claims

claims

1. A method for coating a hard metal or Cermetsubstrat- body by means of a physical vapor deposition (PVD), characterized in that the finished sintered substrate body without further intermediate treatment before the PVD coating of a blast treatment using a granular blasting agent is subjected until the near-surface Zone of the substrate body has an internal stress which is at least substantially equal to the residual stress, which is present in the single or first applied PVD layer.

2. The method according to claim 1, characterized in that the blasting agent has a maximum diameter of 600 microns, preferably at most 150 microns and further preferably at most 100 microns.

3. The method according to claim 1 or 2, characterized in that the substrate body is treated by dry blasting.

4. The method according to any one of claims 1 to 3, characterized in that the blasting agent has at least substantially a roundish grain shape.

5. The method according to any one of claims 1 to 4, characterized in that as blasting agent druckverdüster steel, cast iron granules, heavy metal powder or alloys thereof, glass, corundum, hard metal granules and / or unbreakable ceramics are used.

6. The method according to any one of claims 1 to 5, characterized in that the or the blasting agent by means of compressed air under a pressure of at least 1, 0 x10 ⁵ - 10 x10 ⁵ Pa, preferably 1, 5 x10 ⁵ -3.5 x10 ⁵ Pa are directed to the substrate body.

7. The method according to any one of claims 1 to 6, characterized in that the blasting agent is directed perpendicular to the substrate body surface.

8. The method according to any one of claims 1 to 7, characterized in that the substrate body after the blast treatment with one or more layers of a carbide, nitride, carbonitride, oxide or oxicarbonitride of the elements of the IVa to Vla group of the Periodic Table or AI ₂ O ₃ , AITiN or AIN is coated, wherein the thickness of each individual layer between 0.1 .mu.m and 10 .mu.m and the total thickness is at most 20 microns.

9. Cemented carbide or cermet body provided with a coating, characterized in that the near-surface zones of the substrate body have an internal stress which is at least substantially equal to the residual stress of the single or multiple layers of the first applied PVD layer.

10. Coated carbide or cermet body according to claim 9, characterized in that the body is designed as a cutting tool.