Surface treatment process for mechanical parts subject to wear and corrosion
AssigneeCentre Stephanois de Recherches Mecaniques Hydromecanique et Frottement
InventorsStéphane Chomer, Stephan Teil
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Abstract
In a surface treatment process for mechanical parts, for conferring on the parts a high resistance to wear and corrosion and a roughness propitious to lubrication, nitriding of the part is followed consecutively by oxidation of the part. The nitriding is applied by immersing the part in a molten salt nitriding bath free of sulfur-containing species at a temperature from approximately 500° C. to approximately 700° C. The oxidation is carried out in an oxidizing aqueous solution at a temperature less than approximately 200° C.
Claims19
A surface treatment process for mechanical parts, for conferring on said parts a high resistance to wear and corrosion and a roughness propitious to lubrication, in which process nitriding of said part is followed consecutively by oxidation of said part, said nitriding is applied by immersing said part in a molten salt nitriding bath free of sulfur-containing species at a temperature from approximately 500° C. to approximately 700° C., and said oxidation is carried out in an oxidizing aqueous solution at a temperature less than approximately 200° C., wherein said nitriding bath contains the following ions:
- Li+=2.8-4.2 wt %;
- Na+=16.0-19.0 wt %;
- K+=20.0-23.0 wt %;
- CO32−=38.0-43.0 wt %;
- CNO−=12.0-17.0 wt %;
- and
- with a quantity of CN− not greater than 0.5 wt %.
A surface treatment process for mechanical parts, for conferring on said parts a high resistance to wear and corrosion and a roughness propitious to lubrication, in which process nitriding of said part is followed consecutively by oxidation of said part, said nitriding is applied by immersing said part in a molten salt nitriding bath free of sulfur-containing species at a temperature from approximately 500° C. to approximately 700° C., and said oxidation is carried out in an oxidizing aqueous solution at a temperature less than approximately 200° C., wherein said oxidizing aqueous solution contains the following ions:
- OH−=17-18.5 wt %;
- NO3−=4.0-5.5 wt %;
- NO2−=1.0-2.5 wt %;
- Cl−=0.25-0.35 wt %;
- and
- Na+=25-29 wt %.
A surface treatment process for mechanical parts, for conferring on said parts a high resistance to wear and corrosion and a roughness propitious to lubrication, in which process nitriding of said part is followed consecutively by oxidation of said part, said nitriding is applied by immersing said part in a molten salt nitriding bath free of sulfur-containing species at a temperature from approximately 500° C. to approximately 700° C., and said oxidation is carried out in an oxidizing aqueous solution at a temperature less than approximately 200° C., said molten salt nitriding bath contains the following ions:
- Li+=0.2-10 wt %;
- Na+=10-30 wt %;
- K+=10-30 wt %;
- CO32−=25-45 wt %;
- and
- CNO−=10-40 wt %;
- with a quantity of CN− ions not greater than 0.5 wt %, wherein said oxidizing aqueous solution contains the following ions:
- OH−=10.0-22.0 wt %;
- NO3−=1.8-11.8 wt %;
- NO2−=0-5.3 wt %;
- Cl−=0-1.0 wt %;
- and
- Na+=1.0-38 wt %.
Dependencies are inferred from the claim text.