DE102018111781A1 - Process for coating a substrate material - Google Patents

Abstract

The inventive method for coating a substrate material is characterized by the use of a filler material (same or alien, such as powder, flux cored wire, etc.) as a carrier of CNTs, which is also not directly exposed to the energy source, but introduced into the resulting molten bath and there is melted without damaging the CNTs. By doing so, the thermal stress on the CNTs can be significantly reduced, so that they are not damaged during the coating process and a metal matrix composite material with excellent mechanical properties is produced.

Description

The present invention relates to a method for coating a particular metallic substrate material with disadvantageous mechanical properties.

In the industrial environment, wear protection is a central starting point for avoiding repair work and resulting costs for highly stressed tools. The increase in wear resistance is largely dependent on coating systems that surface reinforce substrate materials lesser mechanical properties. These surface layers are usually hard-reinforced by tungsten-melt-carbide (WSC) or vanadium-carbide (VC) and are generally applied by laser deposition welding, plasma powder build-up welding, or metal inert gas welding (MIG). The high hardness of the hard material particles embedded in a matrix material of high toughness allows effective protection against abrasion and erosion stress.

The use of carbon nanotubes for coatings of metallic materials is also known from the prior art. These carbon nanotubes are characterized by a tubular structure of virtually seamlessly rolled graphene layers and have a variety of outstanding properties, such as an extremely high mechanical strength and exceptional thermal and tribological properties.
For this purpose, it is shown in publication [1] that by using carbon nanotubes (CNTs) as a powder component in thermal spraying processes coatings of increased hardness and wear resistance of steel can be applied. Furthermore, [2] describes the strength-increasing effect of the CNTs in metallic matrix materials, for example aluminum and copper, provided that they are homogeneously distributed in the matrix material. References [3] and [4] show increases in tensile strength, yield strength, modulus of elasticity and hardness for CNT-reinforced aluminum materials. However, the agglomeration of CNTs and carbide formation at elevated process temperatures is also highlighted as a challenge with increasing proportions by weight.

This makes it clear that CNTs can basically be used for material reinforcement, but must be present homogeneously distributed in the composite. In addition, CNTs have some advantages in terms of corrosion and damping properties, since their use reduces the tendency to corrosion [2] and the damping properties of the composite can be significantly improved [5]. Furthermore, improved sliding properties of the coating system can be achieved, which is why there are significant advantages over existing coating systems for wear protection. However, the challenge here is the attachment of the CNTs to the metallic material at the CNT metal matrix interface [2].

Object of the present invention is to provide a method for coating a substrate material, which succeeds in a simple manner, the mechanical properties of a highly stressed substrate material, in particular its wear resistance and its corrosion, damping and sliding properties to improve efficiently.

According to the solution succeeds this task with the features of the first claim.

Advantageous embodiments of the solution according to the invention are specified in the subclaims.

The basic idea of the present invention is the use of carbon nanotubes (CNTs) for increasing the wear resistance of coatings for substrate materials. Starting from the prior art, according to the invention, CNTs should be used as hard-material particles for the production of coating systems by build-up welding, for example for the generation of wear-resistant layers. The use of CNTs requires the avoidance of high thermal stresses and the resulting decomposition of the CNTs, which is why the CNTs must not be exposed directly to the energy source, such as an electric arc or a laser beam.

The inventive method is characterized by the use of a filler material ( 3 ) (same or dissimilar, for example, powder, cored wire, or the like) as a carrier of CNTs, which is also not directly exposed to the energy source, but in the resulting molten bath ( 4 ) and melted there without damaging the CNTs (see 1 ). By doing so, the thermal stress on the CNTs can be significantly reduced, so that they are not damaged during the coating process and a metal matrix composite material with excellent mechanical properties is produced.

Consequently, with the method according to the invention CNTs as hard material particles to increase the wear resistance by increased hardness and strength of the composite at the same time ductile Matrix can be used. Targeted control of the time-temperature regime by the introduction of the CNT-containing filler in the molten bath also allows the targeted distribution of CNTs in the weld, for example by controlling the Schmelzbadkonvektion and the thermal conductivity of the CNTs. By introducing carbon nanotubes into the molten bath, it is furthermore possible to realize a targeted adjustment of a microstructural microstructure in the weld seam, since these act as nucleators and, inter alia, enable targeted, fine-grained microstructural formation. Similarly, the attachment of the CNTs can be improved by incorporation into the molten state of the metal matrix. Finally, an alignment of the CNTs in arc welding processes by the induced magnetic field is conceivable.

In 1 the process of the invention is shown in principle on the example of metal arc welding. In addition to the CNT-containing filler material ( 3 ) another additional filler material ( 2 ) are used without CNTs to increase the material input. However, the use of additional filler metals without CNTs, as in the example of the MSG process, is not absolutely necessary. The thermal energy input can in principle be realized by all methods involving a molten bath ( 4 ) for introducing the filler material ( 3 ) as a carrier for CNTs, for example, arc or blasting method. The filler material (s) can be introduced into the molten bath in the form of flux-cored wire, powder, ribbon or the like.

Bibliography

1. [1] Kaewsai, D .; Watcharapasorn, A .; Singjai, P .; Wirojanupatump, S .; Niraanatlumpong, P .; Jiansirisomboon, S .: Thermal sprayed stainless steel / carbon nanotube composite coatings., In: Surface & Coatings Technolgy, No. 205, pp. 2104-2112, 2010 ,
2. [2] Bakshi, SR; Lahiri, D .; Agarwal, A .: Carbon nanotube reinforced metal matrix composites - a review., In: International Materials Reviews, No. 1, Vol. 55, pp. 41-64, 2010 ,
3. [3] Esavi, AMK; EI Borady, MA: Carbon nanotube-reinforced aluminum strips. In: Composites Science and Technology, No. 68, pp. 486-492, 2008 ,
4. [4] Wu, J .; Zhang, H .; Zhang, Y .; Wang, X .: Mechanical and thermal properties of carbon nanotube / aluminum composites consolidated by spark plasma sintering. In: Materials and Design, No. 41, pp. 344-348, 2012 ,
5. [5] Deng, CF; Wang, DZ; Zhang, XX; Ma, YX: Damping characteristics of carbon nanotube reinforced aluminum composite., In: Materials Letters, No. 61, pp. 3229-3231, 2007 ,

LIST OF REFERENCE NUMBERS

1 -

MSG power source

2 -

Additional material

3 -

Additional material with CNTs

4 -

melting bath

5 -

order weld

6 -

Electric arc

7 -

Substrate material

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Kaewsai, D .; Watcharapasorn, A .; Singjai, P .; Wirojanupatump, S .; Niraanatlumpong, P .; Jiansirisomboon, S .: Thermal sprayed stainless steel / carbon nanotube composite coatings., In: Surface & Coatings Technolgy, No. 205, pp. 2104-2112, 2010 [0010]
• Bakshi, S. R .; Lahiri, D .; Agarwal, A .: Carbon nanotube reinforced metal matrix composites - a review., In: International Materials Reviews, No. 1, Vol. 55, pp. 41-64, 2010 [0010]
• Esawi, A.M.K .; EI Borady, M.A.: Carbon nanotube-reinforced aluminum strips. In: Composites Science and Technology, No. 68, pp. 486-492, 2008 [0010]
• Wu, J .; Zhang, H .; Zhang, Y .; Wang, X .: Mechanical and thermal properties of carbon nanotube / aluminum composites consolidated by spark plasma sintering. In: Materials and Design, No. 41, pp. 344-348, 2012 [0010]
• Deng, C.F .; Wang, D.Z .; Zhang, X.X .; Ma, Y. X .: Damping characteristics of carbon nanotube reinforced aluminum composite., In: Materials Letters, No. 61, pp. 3229-3231, 2007 [0010]

Claims (5)

Method for coating a substrate material (7), in which at least one filler material (3) is applied to the surface of the substrate material (7) to be coated by a locally limited and locally variable thermal energy input, the filler material (3) having a proportion of carbon nanotubes and is introduced and melted in a melt formed by the thermal energy input (4) while avoiding interaction with the energy carrier. Method according to Claim 1 in which the filler material (3) contained in the carbon nanotubes is fed to the molten bath (4) as a filler wire, as a powder or as a ribbon. Method according to one of Claims 1 or 2 , wherein several similar and / or non-related filler materials are used. Method according to one of Claims 1 to 3 in which the introduction of the filler material (3) contained in the carbon nanotubes into the molten bath (4) is controlled by means of a defined time-temperature regime. Method according to one of Claims 1 to 4 in which the thermal energy input is realized by means of an arc (6), wherein the carbon nanotubes contained in the filler material (3) are aligned by means of the magnetic field generating the arc (6).

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