Search

EP-4735539-A1 - METHOD FOR SURFACE TREATMENT OF A STEEL MECHANICAL PART TO IMPROVE ITS RESISTANCE TO WEAR AND CORROSION, UNDER HARSH STRESSES

EP4735539A1EP 4735539 A1EP4735539 A1EP 4735539A1EP-4735539-A1

Abstract

The invention relates to a method for surface treatment of a steel mechanical part in order to improve its wear and corrosion resistance, the method comprising at least one step of nitriding or nitrocarburizing the part, forming a nitrided surface layer, followed by a step of impregnating the nitrided surface layer with a solution comprising at least one hydrophobic wax, characterized in that said wax is a carbon-containing organic compound of which the molecular weight is less than 500, and preferably between 200 and 500.

Inventors

  • Magdinier, Pierre Louis
  • MONTEUX, Vincent

Assignees

  • HYDROMECANIQUE ET FROTTEMENT

Dates

Publication Date
20260506
Application Date
20240619

Claims (13)

  1. [Claims 1] Method for surface treatment of a mechanical steel part to improve its resistance to wear and corrosion, the method comprising at least one step of nitriding or nitrocarburizing the part forming a nitrided surface layer, followed by a step of impregnating the nitrided surface layer with a solution comprising at least one hydrophobic wax, characterized in that said wax is an organic carbon compound whose molecular weight is less than 500, and preferably between 200 and 500.
  2. [Claims 2] Method according to claim 1, characterized in that the nitriding or nitrocarburizing step is followed by an oxidation step.
  3. [Claims 3] Method according to one of the preceding claims, characterized in that the impregnation is carried out by dipping in a solution bath or by spraying the solution, at room temperature.
  4. [Claims 4] Method according to claim 3, characterized in that the impregnation is carried out by soaking in a solution bath for a period of at least 2 min.
  5. [Claims 5] Method according to one of the preceding claims, characterized in that the impregnation is carried out with a solution comprising the wax and a solvent diluting the wax to 50% to 75% or to 80%.
  6. [Claims 6] Method according to one of the preceding claims, characterized in that it then comprises a step of air drying the impregnated solution, for at least 5 min, and at room temperature.
  7. [Claims 7] Method according to one of the preceding claims, characterized in that the solution comprises calcium sulfonate, in an amount of between 1 and 30% by mass.
  8. [Claims 8] Method according to one of the preceding claims, characterized in that the solution comprises the wax which is essentially composed of an alkane cut from C20 to C35, and calcium sulfonate.
  9. [Claims 9] Method according to one of the preceding claims, characterized in that the solution comprises 1,1'-Biphenyl 4,4'-dibromo of formula C12H8Br2.
  10. [Claims 10] Mechanical part made of steel having undergone a surface treatment to improve its resistance to wear and corrosion, the part having a nitrided surface layer impregnated with a layer of a hydrophobic wax-based solution, characterized in that the wax is an organic carbon compound whose molecular weight is less than 500, and preferably between 200 and 500.
  11. [Claims 11] Mechanical part according to claim 10, characterized in that the wax-based solution layer has a surface mass of between 5 and 60 g/m 2 .
  12. [Claims 12] Mechanical part according to one of claims 10 to 11, characterized in that the layer of wax-based solution comprises calcium sulfonate, in an amount of between 1 and 30% by mass.
  13. [Claims 13] Mechanical part according to one of claims 10 to 12, characterized in that the layer of wax-based solution comprises the wax which is essentially composed of an alkane cut from C20 to C35, and calcium sulfonate.

Description

Description Title of the invention: Method for surface treatment of a mechanical steel part to improve its resistance to wear and corrosion, under severe constraints Technical field [0001] The present invention relates to the field of surface treatment of mechanical steel parts, aimed at improving their resistance to wear and corrosion. More specifically, the invention relates to a treatment method involving nitriding or nitrocarburizing, optionally followed by oxidation, and impregnation with a hydrophobic wax. Prior art [0002] Document EP0524037 teaches a surface treatment method for improving the corrosion resistance of mechanical parts. [0003] This document describes a technique for improving the friction and corrosion resistance properties of ferrous metal parts. The disclosed technique involves a series of treatments, including nitriding, oxidation and the application of a final coating. [0004] This final coating is a hydrophobic wax, a high molecular weight organic carbon compound, in particular between 500 and 10,000. The application of this high molecular weight wax helps to improve the corrosion resistance of the parts and to minimize rebound effects. [0005] These treatments have the advantage of being inexpensive and easy to implement, even for industrial production on mass-produced parts. In addition, they give the treated parts high technical performance even when these parts are of complex shapes. [0006] Document WO2016/102813 presents a process using PVD coating to increase the durability of mechanical parts. [0007] This document describes a method for treating the surface of a steel mechanical part in order to give it high resistance to wear and corrosion. The process involves the following steps: - a nitriding or nitrocarburizing step to form a layer of iron nitrides at least 8 micrometers thick; - an oxidation step to generate a layer of oxides with a thickness of between 0.1 and 3 micrometers; - an impregnation step by soaking in an impregnation bath for at least 5 minutes. This bath is formed of at least 70% by weight, to within 1%, of a hydrocarbon solvent, from 10% to 30% by weight, to within 1%, of at least one paraffin oil and at least one additive of the synthetic phenolic additive type at a concentration of between 0.01% and 3% by weight, to within 0.1%. [0008] This method provides a substantial improvement in corrosion resistance compared to a conventional bath based on oils, acids and ethanol. In addition, the treated parts are dry to the touch, meaning they do not transfer oil to another surface and do not pick up surrounding dust. This also gives them the ability to undergo post-treatment, such as overmolding. [0009] However, with either of the above techniques, if the treated and impregnated part is subjected to so-called severe constraints, such as high-pressure washing or repeated mechanical stresses, such as friction by a seal for example, then the corrosion resistance is degraded. [0010] To overcome this problem, it is known to use special coating technologies, such as electroless nickel plating or a hard chrome coating. However, these techniques have certain drawbacks, including: - fluctuating raw material costs: Nickel, for example, is subject to significant price fluctuations due to various economic and geopolitical factors. This can make the cost of coating operations difficult to predict and potentially more expensive; - REACH regulations: The European Regulation on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) requires prior authorisation for the use of certain materials, such as hard chrome. This can slow down the production process and increase costs. Additionally, there are also environmental and health concerns associated with the use of these substances. [0011] Therefore, although these coating technologies can improve the wear and corrosion resistance of steel mechanical parts, they have their own challenges in terms of cost and regulatory compliance. [0012] Also known is document FR3030578 which describes the current state of the art. Disclosure of the invention [0013] One of the aims of the invention is to overcome the drawbacks of the prior art, by proposing a method of surface treatment of a mechanical steel part to improve its resistance to wear and corrosion, which makes it possible to guarantee this resistance even when the part is subjected to aggressive and severe environmental conditions, such as repeated washing under high-pressure water jets, exposure to sand and bad weather, or repeated mechanical friction. [0014] The present invention aims to solve the problems of the prior art by proposing a method for surface treatment of a mechanical part made of steel to improve its resistance to wear and corrosion. The method comprises at least one nitriding or nitrocarburizing step, forming a nitrided surface layer, consisting for example of a compact deep sub-layer and a porous surface sub-layer. The surface sub-layer co