DE19733306C1 - Iron-based additive material is used for thermal coating of components exposed to friction - Google Patents

Abstract

An iron-based thermal coating material comprises (by wt.) 15-40% Mn, 0.1-30% Cr, 0.1-8% Si, 0.1-6% Ni, <= 1% Al, <= 0.2% C, 0.5-7% B, <= 0.05% S, <= 0.05% P, \}12% total additions of <= 5% Mo, <= 5% Ti, <= 6% Nb, <= 6% V and <= 12% W, balance Fe and impurities. An additive material, in the form of a mixture, a gas atomized alloy, an agglomerated metal powder, a core-filled wire, a core-filled strip, a sintered strip or a cast sheathed rod electrode and used for thermal coating of components exposed to friction, comprises (by wt.) 15-40% Mn, 0.1-30% Cr, 0.1-8% Si, 0.1-6% Ni, <= 1% Al, <= 0.2% C, 0.5-7% B, <= 0.05% S, <= 0.05% P, \}12% total additions of <= 5% Mo, <= 5% Ti, <= 6% Nb, <= 6% V and <= 12% W, balance Fe and impurities. Independent claims are also included for (i) use of the above additive material for applying a layer consisting of a matrix of metastable austenite and optionally hexagonal iota martensite and alpha ' martensite, together with hard borides and less than 10 vol.% hard carbides; (ii) use of a preferred additive material, of composition (by wt.) 20-25% Mn, 13-20% Cr, 0.1-2% Ni, 3-6% W, 0.1-0.15% C, 1.5-2.5% B, balance Fe and impurities, for applying a low friction and low wear layer for a sliding component pairing with good fatigue and impact resistance; and (iii) use of another preferred additive material, of composition (by wt.) 18-25% Mn, 13-25% Cr, 0.1-2% Ni, 3-5% W, 0.1-0.15% C, 4-6% B, balance Fe and impurities, for applying a low friction layer with high abrasion resistance and higher thermal loading capacity.

Description

The invention relates to an additional material for thermal coating tribologically as well thermally and chemically stressed components of machine, apparatus and plant construction it.

In the case of metallic friction pairings with solid-state contact, the stressed areas become to increase wear resistance in many cases by coating with hard Armored materials. For thermo-mechanically highly loaded sliding pairings in Ma Machine and plant engineering mostly uses cobalt (stellite) or nickel hard alloys (Tab. 1), whereby the cobalt hard alloys have a better friction behavior. Disadvantage of this Alloys are their high material price and health risks for men that result from your use. Nickel fumes are carcinogenic and cobalt or cobalt alloys are in nuclear plants due to the formation of long-lived radioactive Isotopes Co 60 cannot be used. Hard iron-based alloys are cheaper, but are preferred for abrasive loading because of their high susceptibility to brittle fracture claims used. In terms of friction behavior, they are significantly lower than Co hard alloys lay. Their corrosion resistance is against the cobalt and nickel hard alloys worse.

The invention is based, an inexpensive iron-based additional material the task for thermal coating of tribologically stressed components to specify the training formation of a low-friction and low-wear hard alloy with good corrosion properties enables, the metal matrix of metastable austenite and hexagonal ε-martensite exists and therefore has the same friction behavior as with hard alloys based on cobalt (Stellite) is reached.

This object is achieved according to the invention by means of an additional material according to claim 1. The basic idea of the invention is that the layer produced by cladding, spraying or other thermal coating processes is a hard alloy or a composite of a metastable austenitic FeMn or FeMnCr metal matrix with embedded boride hard materials ( Figure 1). Coatings, which are produced with means of the additional material according to the invention, thus make it possible to increase the utility value and the service life of components which are contaminated with reife, e.g. B. Sitzflä Chen of pipe slides or valves in internal combustion engines or Aktivkompo components in extruders. The additional material for the production according to the invention of a wear and corrosion-resistant layer consists of the following components in percent by weight, based on the percent by mass:
15-40% Mn,
0.1-30% Cr,
0.1-8% Si,
0.1-6% Ni,
≦ 1% Al,
≦ 0.2% C,
0.5-7% B,
≦ 0.05% S,
≦ 0.05% P,
and additions of
≦ 5% Mo,
≦ 5% Ti,
≦ 6% Nb,
≦ 6% V,
≦ 12% W,
together up to a maximum of 12%, balance Fe, including unavoidable metallurgical impurities.

The additional material is either a powder mixture, a gas-atomized alloy, an agglo merized metal powder, a cored wire or filler tape, a sintered tape or a cast, um covered stick electrode.

The metallic matrix, the heart of a hard alloy, has to meet additional requirements in addition to the firm embedding of the hard materials, which are carriers of a high hardness of the composite:

• - mechanical stability and ductility (high mixed crystal hardness, high fracture toughness),  
• - thermal stability (high melting point, good thermal conductivity, low heat levels strain),
• - chemical and electrochemical resistance,
• - good friction and wear behavior.

Compared to commercially available hard alloys, the special advantage of the hard alloys produced according to the invention results from the thermodynamic instability of austenite, but depending on the manganese content also of ε-martensite, the metallic matrix in the alloy range between 10 and 30% manganese, up to 15% chromium and carbon ≦ 0.15% ( Figure 2). This matrix, which is deliberately metallurgically designed for this state, then tends to undergo martensitic phase transformations γ - <(ε) - <α 'and γ - <ε under tribomechanical loading. The associated property changes:

• - increase in strength
  Formation of tribomechanically induced α'- and ε-martensite in surface areas with high stress,
  Development of residual compressive stresses during α'-martensite formation,
• - Improvement of fracture toughness
  Generation and movement of the transformation dislocations necessary for the formation of martensite in the metal matrix (transformation plasticity),
• - Reduction of friction by ε-martensite formation
  low shear strength between the base planes of the hexagonal atomic cell and twisting of the base planes (friction texture) parallel to the surface exposed to friction,
• - Increasing energy dissipation
  The amount of energy required for the change in shape and volume of the martensite is extracted from the energy introduced by friction and released to the environment in the form of conversion heat and is therefore no longer available, particularly in the case of fatigue-like material damage,

which improve the friction and wear behavior of the matrix (

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2 in the range of 15 up to 30% Mn as well

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3 using the example of FeMn20Cr12), allow in context with the borid hard phases the formation of a surface structure with tribological suitable property profile. The hard material produced according to the invention thus have layers or hard alloys with metastable austenitic FeMn base compared to the hard alloy manufactured with commercially available additional materials based on Co and Ni  a better but at least equivalent tribo behavior with lower material costs on.

In a particularly preferred embodiment of the additional material with the chemical composition:
20-22% Mn,
13-18% Cr,
0.1-2% Ni,
3-5% W,
0.1-0.15% C,
1.5-2.5% B,
Rest of iron
a corrosion-resistant layer with good friction behavior can be produced, in the tough metal matrix consisting of metastable austenite and hexagonal ε-martensite, chromium-rich mixed borides are embedded. This additional material is ideally suited for the plating of sealing surfaces in pipeline valves or valves in internal combustion engines. Tab. 2 to 4 show the tribological performance of the hard alloy according to the invention (FeMnCrWB) compared to commercially available hard metals based on Ni and Co guided.

For applications with additional abrasive stress on the component, e.g. B. for the Pan of active components in extruders or in crushing plants of building material recycling, is another embodiment of the additional material with the chemical composition:
20-22% Mn,
15-20% Cr,
0.1-2% Ni,
3-5% W,
0.1-0.15% C,
3-5% B,
advantageously suitable. The high proportion of hard materials (primary borides) formed by the higher boron content in the applied layer improves the abrasion resistance of this tough hard alloy, so that there is an increase in performance which increases the tribological performance of commercially available hard alloys, such as the expensive Ni and Co base alloys or the mostly very hard and therefore crack-sensitive Fe-based alloys, at least reached.

Tab. 2: Chemical composition of the hard alloys examined (in percent by mass)

Tab. 3: Mineral sliding wear w 'of hard alloys (test conditions see Figure 4)

Tab. 4: Friction µ and wear w 'of hard alloys at temperatures of 20 and 500 ° C (dry oscillating sliding friction, test conditions see Figure 4)

Claims (7)

1. Additional material in the form of a mixture, a gas atomized alloy, an agglomerated metal powder, a cored wire, a filler tape, a sintered tape or a cast coated stick electrode for the thermal coating of tribologically stressed components, in particular by means of spray application or buildup welding, characterized in that it consists of the following components in percent by mass, based on the overall analysis, there is:
15 to 40% Mn,
0.1 to 30% Cr,
0.1 to 8% Si,
0.1 to 6% Ni,
≦ 1% Al,
≦ 0.2% C,
0.5 to 7% B,
≦ 0.05% S,
≦ 0.05% P,
and additions of
≦ 5% Mo,
≦ 5% Ti,
≦ 6% Nb,
≦ 6% V,
≦ 12% W,
together up to a maximum of 12%, balance Fe, including inevitable metallurgical impurities. 2. Additional material according to claim 1, consisting of the components, based on the overall analysis in percent by mass:
20 to 25% Mn,
13 to 20% Cr,
0.1 to 2% Ni,
3 to 6% W,
0.1 to 0.15% C,
1.5 to 2.5% B,
Balance Fe, including unavoidable metallurgical contaminants. 3. Additional material according to claim 1 consisting of the components, based on the overall analysis in percent by mass:
18 to 25% Mn,
13 to 25% Cr,
0.1 to 2% Ni,
3 to 5% W,
0.1 to 0.15% C,
4 to 6% B,
Balance Fe, including unavoidable metallurgical contaminants. 4. Additional material according to one of claims 1 to 3, characterized in that the core of the cored wire or the filler tape in addition to the alloy components Flux components in proportions of 6-10% based on the overall analysis contains. 5. Use of additional material according to claim 1 or 4 for applying a layer that a composite of a metal matrix consisting of metastable austenite metastable austenite and hexagonal ε-martensite or made of metastable austenite, hexagonal ε-martensite and α'-martensite, and boride hard materials but less than 10% by volume of carbide hard materials. 6. Use of an additional material according to claim 2 or 4 for applying a friction and low-wear layer in sliding pairings with good resistance to fatigue and shock-like material stress. 7. Use of an additional material according to claim 3 or 4 for applying a low-friction layer with high abrasion resistance and high thermal resilience.