NEW PRODUCT AND USE THEREOF

Abstract

The present invention relates to a new pre-alloyed metal based powder, intended to be used in surface coating of metal parts. The powder is deposited using e.g. laser cladding or plasma transfer arc welding (PTA), or thermal spray (e.g. HVOF). The powder is useful for reducing friction and improving wear reducing properties of the deposited coating. Such coatings may also improve machinability. As friction or wear reducing component, inclusions of manganese sulphide or tungsten sulphide in the pre-alloyed powder may be used.

Claims

1. A powder mixture containing: i) atomised metal powder having the following composition: C, 0.05-0.5%; Si, 2.0-4.0%; B, 0.8-1.3%; Cr, 2-10%; Fe, 3-15%; Al, 0.3-0.5%; Mn, 5-15%; the balance being Ni, ii) atomised metal powder having the following composition: C, 0.05-0.2%; Si, 2.2-2.9%; B, 0.8-1.3%; Cr, 2.8-3.45%; Fe, 1.4-2.3%; Al, 0.3-0.5%; S, 3-13%; the balance being Ni, and iii) atomised metal powder having the following composition: C, 0.2-0.27%; Si, 3.5%; B, 1.6; Fe, 2.5; Cr, 7.5; the balance being Ni.

2. The powder mixture according to claim 1, wherein the ratio between the powders are such that the amount of MnS is 4-15%.

3. A metal powder according to claim 1, wherein the particle size of the prealloyed powder is from 45 m to 200 mm.

4. A method for surface coating metal parts, by way of laser cladding or PTA (plasma transferred arc), with a metal powder according to claim 1 thereby producing a metal coated component.

Description

FIGURES

[0013] FIG. 1 Wear rate vs. sliding velocity for S-powder clad pin and carbon steel pin for Hertzian max. contact pressure of 500 MPa.

[0014] FIG. 2 Wear rate vs. sliding velocity for S-powder clad pin and carbon steel pin for Hertzian max. contact pressure of 1000 MPa.

[0015] FIG. 3 SEM micrograph of S-powder clad, top of the micrograph is wear test surface.

[0016] FIG. 4 SEM micrograph of S-powder clad, top of the micrograph is wear test surface.

DETAILED DESCRIPTION

[0017] All percentages herein, and in the claims are % by weight.

[0018] The invention is a powder mixture containing; [0019] i) atomised metal powder having the following composition; C, 0.05-0.5%; Si, 2.0-4.0%; B, 0.8-1.3%; Cr, 2-10%; Fe, 3-15%; Al, 0.3-0.5%; Mn, 5-15%; the balance being Ni; [0020] ii) atomised metal powder having the following composition; C, 0.05-0.2%; Si, 2.2-2.9%; B, 0.8-1.3%; Cr, 2.8-3.45%; Fe, 1.4-2.3%; Al, 0.3-0.5%; S, 3-13%; the balance being Ni; [0021] iii) atomised metal powder having the following composition; C, 0.2-0.27%; Si, 3.5%; B, 1.6; Fe, 2.5; Cr, 7.5; the balance being Ni.

[0022] Further, the invention is a powder mixture according to the above, wherein the ratio between the powders are such that the amount of MnS is 4-15%.

[0023] Further, the invention is a metal powder according to the above, wherein the particle size of the prealloyed powder is from 45 m to 200 mm, or from 50-150 m.

[0024] The invention is also a method for surface coating metal parts, by way of laser cladding or PTA (plasma transferred arc), with a metal powder according to the above, thereby producing a metal coated component.

[0025] It is previously known that solid lubricants such as MnS or WS are useful in the field of surface coating, whereby a hard phase is formed on the surface of a substrate. MnS or WS function as a so-called solid lubricant. The present inventor has shown that a mixture of metal powders can be used in a surface coating procedure, such as plasma transfer arc, and by choosing the right components in the individual metal powders, the solid lubricant can form in the resulting surface coating or hard phase. The metal powders may be nickel, cobalt, or iron based.

[0026] Three atomised metal powders are used in the mixture according to the invention; In one embodiment, Powder M may have the following composition; C, 0.05-0.5%; Si, 2.0-4.0%; B, 0.8-1.3%; Cr, 2-10%; Fe, 3-15%; Al, 0.3-0.5%; Mn, 5-15%; the balance being Ni. The powder was prepared by atomisation of a melt containing the elements above in said amounts. The resulting powder contains Mn as inclusions in a matrix of metal alloy. This powder is herein denoted Powder M;

[0027] Powder S may have the following composition; C, 0.05-0.2%; Si, 2.2-2.9%; B, 0.8-1.3%; Cr, 2.8-3.45%; Fe, 1.4-2.3%; Al, 0.3-0.5%; S, 3-13%; the balance being Ni. The powder was prepared by atomisation of a melt containing the elements above in said amounts. The resulting powder contains S as inclusions in a matrix of metal alloy. This powder is herein denoted Powder S; and the third powder is 1540a standard grade. This powder is herein denoted Powder MP.

[0028] Powder S, Powder Mn and powder P are mixed, in order to achieve 4-15% MnS in the final melt pool which forms in the below mentioned cladding methods. This powder mixture is herein denoted Mixture PM.

[0029] The Mixture PM is especially well suited for weld cladding methods, such as laser cladding or PTA. In addition, thermal spray, e.g. flame spray, HVOF, HVAF, coldspray, plasma spray, and the like may also be suitable applications.

[0030] The prealloyed nickel, iron, or cobalt based powder is preferably produced by water or gas atomization of a melt which includes Mn, W, or S and other alloying elements chosen from the group consisting of C, Si, B, Cr, Fe, Al, Ni, Co, and V.

[0031] The particle size of the pre-alloyed powder alloy is typically from 10 m to 800 m, or from 10 m to 200 m, or preferably from 15-150 m, or 50-150 m.

[0032] In one aspect, the invention provides a method for surface coating metal parts, by way of deposition techniques such as laser cladding or PTA (plasma transferred arc); thermal spray methods such as HVOF (high velocity oxy fuel spray), HVAF (high velocity acetylene fuel spray) or plasma spray; or by slurry methods such as centrifugal casting, with the above mentioned metal powder.

[0033] In a further aspect, the invention also provides metal parts produced by the above mentioned suitable for coating by the powder according to the invention for dry friction contacts in machinery, such as e.g. industrial valves, sheet metal forming (SMF) tools, transport rollers in iron works, paper knives, and glass moulds.

EXAMPLES

Example 1

[0034] Preparation of Pre-alloyed Powder

[0035] A metal powder with the following composition; C, 0.05-0.5%; Si, 2.0-4.0%; B, 0.8-1.3%; Cr, 2-10%; Fe, 3-15%; Al, 0.3-0.5%; Mn, 5-15%; the balance being Ni, was prepared by atomisation of a melt containing the elements above in said amounts. The resulting powder contains Mn as inclusions in a matrix of metal alloy. This powder is herein denoted Powder M.

[0036] An additional metal powder with the following composition; C, 0.05-0.2%; Si, 2.2-2.9%; B, 0.8-1.3%; Cr, 2.8-3.45%; Fe, 1.4-2.3%; Al, 0.3-0.5%; S, 3-13%; the balance being Ni, was prepared by atomisation of a melt containing the elements above in said amounts. The resulting powder contains S as inclusions in a matrix of metal alloy. This powder is herein denoted Powder S.

[0037] 1540a standard grade This powder is herein denoted Powder M P.

[0038] Powder S, Powder Mn and powder P are mixed, 3MA powder mix, in order to achieve 4-15% MnS.

Example 2

[0039] Application of Powder by Deposition using PTA

[0040] Pre-alloyed or pre-mixed powder was applied to test samples as follows; Powder A was deposited onto S235JRG (base structural steel) substrate plates by PTA (plasma transfer arc) with parameters set to allow for a dilution of 5-15%.

Example 3

[0041] Powder S was spread by hand on substrate as a powder before fusing with the substrate. How was the powder fuwed?

Example 4

[0042] Powder according to the invention was also applied to substrate by laser cladding. The coating from Powder S appears to result in finer inclusion sizes of MnS than when applied by PTA.

Example 5

[0043] Block on ring wear testing was performed, and shows the beneficial effects of 3MA powder mix in a metal surface coating layer or clad. The specimens were rectangular blocks 101050 mm where the base metal was commonly used low carbon structural steel (EN S235 JRG, ASTM A570 Gr.36) and the surface layer was at least 0.5 mm thick in the as finished measure. The test surface had a ground finish with surface roughness of Ra 0.3-0.4 m, prepared by grinding. The counter rings 60/R1002016 mm were made of UIC 900A rail steel. The test was unlubricated i.e. dry, and the test samples were carefully cleaned and then degreased by ethanol prior to testing. The testing was performed as a wear mechanism mapping trial. The test normal load was 5 and 42 N what correspond 500 respective 1000 MPa in max. Hertzian contact pressure. Sliding velocity was 0.045, 0.13, 0.37, 1.1 and 2.9 m/s. The total sliding distance was 800 m. Results are shown in FIG. 1 and FIG. 2 for contact pressures of 500 respective 1000 MPa. FIG. 3 and FIG. 4 illustrate microstructure of S-powder laser clad.