Method for surface treatment of a steel component by nitriding or nitrocarburising, oxidising and then impregnating

Patent metadata

Field	Value
Publication number	US-10774414-B2
Application number	US-201515538005-A
Country	US
Kind code	B2
Filing date	Dec 15, 2015
Priority date	Dec 23, 2014
Publication date	Sep 15, 2020
Grant date	Sep 15, 2020

Abstract

Disclosed is a method for surface treatment of a steel component, providing high resistance to wear and corrosion, including nitriding or nitrocarburising to form a compound layer with a thickness of at least 8 micrometers made up of iron nitrides having phases ε and/or γ′, oxidizing to generate a layer of oxides with a thickness of 0.1-3 micrometers, and soaking in an impregnation bath during at least 5 minutes at room temperature, the bath being made up of at least 70 wt %, ±1%, of a solvent made up of a mixture of hydrocarbons formed by a C9 to C17 alkane fraction, 10 to 30 wt %, ±1%, of at least one paraffin oil formed by a C16 to C32 alkane fraction, and at least one additive such as a synthetic phenolic additive with a concentration of 0.01 to 3 wt %, ±0.1%.

First claim

The invention claimed is:

1. A method of surface treatment of a steel part to give it a high resistance to wear and to corrosion comprising
a step of nitriding or of nitrocarburizing adapted to form a combination layer of at least 8 micrometers thickness formed of iron nitrides of ε and/or γ′ phases,
an oxidizing step adapted to generate a layer of oxides of thickness comprised between 0.1 and 3 micrometers and
a step of impregnating by steeping in an impregnation bath for at least 5 minutes, said bath being formed of at least 70% by weight, to the nearest 1%, of a solvent formed of a mixture of hydrocarbons formed of a set of alkanes from C9 to C17, of 10% to 30% by weight, to the nearest 1%, of at least one paraffin oil composed of a set of alkanes from C16 to C32 and of at least one additive of synthetic phenolic additive type at a concentration comprised between 0.01% and 3% by weight, to the nearest 0.1%, at ambient temperature.

2. A method according to claim 1 , wherein the synthetic phenolic additive is a compound of formula C 15 H 24 O.

3. A method according to claim 2 , wherein the impregnation bath is formed of 90%+/−0.5% by weight of solvent, 10%+/−0.5% by weight of paraffin oils and between 0.01% and less than 1%+/−0.1%, of synthetic phenolic additive of formula C 15 H 24 O.

4. A method according to claim 1 , wherein the impregnation bath further comprises at least one additive chosen from the group constituted by calcium or sodium sulfonate, phosphites, diphenylamines, zinc dithiophosphate, nitrites, phosphoramides.

5. A method according to claim 1 , wherein the steeping operation is followed by an operation of natural drying or drying that is accelerated by baking.

6. A method according to claim 1 , wherein the nitriding or nitrocarburizing step is carried out in a bath of molten salts containing from 14% to 44% by weight of alkali metal cyanates at a temperature of 550° C. to 650° C. for at least 45 minutes.

7. A method according to claim 6 , wherein the nitriding/nitrocarburizing bath contains from 14% to 18% by weight of alkali metal cyanates.

8. A method according to claim 6 wherein the nitriding/nitrocarburizing treatment is carried out at a temperature of 590° C. for 90 minutes to 100 minutes.

9. A method according to claim 6 wherein the nitriding/nitrocarburizing treatment is carried out at a temperature of 630° C. for approximately 45 minutes to 50 minutes.

10. A method according to claim 1 , wherein the nitrocarburizing step is carried out in a gaseous medium between 500° C. and 600° C. containing ammonia.

11. A method according to claim 1 , wherein the nitriding or nitrocarburizing step is carried out in an ionic medium forming a plasma, comprising at least nitrogen and hydrogen at low pressure.

12. A method according to claim 1 , wherein the nitriding or nitrocarburizing step is carried out so as to form a combination layer of thickness at least 10 micrometers.

13. A method according to claim 1 , wherein the oxidizing step is carried out in a bath of molten salts which contains alkali metal nitrates, alkali metal carbonates and alkali metal hydroxides.

14. A method according to claim 13 , wherein the oxidizing step is carried out at a temperature of 430° C. to 470° C. for 15 to 20 minutes.

15. A method according to claim 1 , wherein the oxidizing step is carried out in an aqueous bath which contains alkali metal hydroxides, alkali metal nitrates and alkali metal nitrites.

16. A method according to claim 15 , wherein the oxidizing step is carried out at a temperature of 110° C. to 130° C. for 15 to 20 minutes.

17. A method according to claim 1 , wherein the oxidizing step is carried out in a gaseous medium for the most part constituted by water vapor, at a temperature of 450° to 550° for 30 to 120 minutes.

18. A method according to claim 2 , wherein the impregnation bath further comprises at least one additive chosen from the group constituted by calcium or sodium sulfonate, phosphites, diphenylamines, zinc dithiophosphate, nitrites, phosphoramides.

19. A method according to claim 3 , wherein the impregnation bath further comprises at least one additive chosen from the group constituted by calcium or sodium sulfonate, phosphites, diphenylamines, zinc dithiophosphate, nitrites, phosphoramides.

20. A steel part having a high resistance to wear and to corrosion, the steel part comprising:
a combination layer of at least 8 micrometers;
a layer of oxides of thickness comprised between 0.1 and 3 micrometers; and
an impregnation layer which is dry to the touch, the impregnation layer comprising at least one synthetic phenolic additive.

21. The steel part according to claim 20 , wherein the combination layer is formed of iron nitrides of ε and/or γ′ phases.

22. The steel part according to claim 20 , wherein the combination layer has a thickness of at least 10 micrometers.

23. The steel part according to claim 22 , wherein the combination layer has a thickness comprised between 10 μm and 25 μm.

24. The steel part according to claim 20 , wherein the impregnation layer comprises at least one paraffin oil composed of a set of alkanes from C16 to C32.

25. The steel part according to claim 20 , wherein the at least one synthetic phenolic additive is represented by formula C 15 H 24 O.

26. The steel part according to claim 20 , wherein the impregnation layer further comprises at least one additive selected from the group consisting of calcium sulfonate, sodium sulfonate, phosphites, diphenylamines, zinc dithiophosphate, nitrites, and phosphoramides.

Assignees

• Hydromecanique & Frottement

Inventors

• Magdinier Pierre-Louis
• Desbouche-Janny Marie-Noelle

Classifications

• C21D1/06

  Surface hardening · CPC title

• C23C8/34

  more than one element being applied in more than one step · CPC title

• C23C8/58 Primary

  more than one element being applied in more than one step · CPC title

• C23C8/02

  Pretreatment of the material to be coated (C23C8/04 takes precedence) · CPC title

• C23C8/80 Primary

  After-treatment · CPC title