Method of fabricating a nitrided low-alloy steel part

Patent metadata

Field	Value
Publication number	US-10344370-B2
Application number	US-201615042196-A
Country	US
Kind code	B2
Filing date	Feb 12, 2016
Priority date	Feb 13, 2015
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

A method of fabricating a nitrided low-alloy steel part, includes a) decarburizing the surface of a low-alloy steel part including at least one alloying element that is both nitride-forming and carbide forming in order to obtain a decarburized part presenting a carbon-depleted surface layer of thickness less than or equal to 1.5 mm, the minimum content of carbon by weight in the carbon-depleted surface layer being less than or equal to 70% of the carbon content by weight in the core of the decarburized part; b) treating the decarburized part with quenching treatment followed by annealing treatment; and c) nitriding the carbon-depleted surface layer in order to obtain a nitrided low-alloy steel part, step c) being performed after step b).

First claim

The invention claimed is:

1. A method of fabricating a nitride low-alloy steel part, the method comprising:
a) decarburizing the surface of a low-alloy steel part including at least one alloying element that is both nitride-forming and carbide-forming in order to obtain a decarburized part presenting a carbon-depleted surface layer beginning from the surface to a depth of less than or equal to 1.5 mm, wherein the minimum content of carbon by weight, C minimumcarbondepletedsurfacelayer , in the carbon-depleted surface layer is defined as follows:
0.05 wt %≤C minimumcarbondepletedsurfacelayer ≤0.7*C carboncore

wherein C carboncore is the carbon content by weight in the core of the decarburized part, and wherein the maximum content of carbon by weight in the carbon-depleted surface layer is less than or equal to 0.45%;
b) treating the decarburized part with quenching treatment followed by tempering treatment; and
c) nitriding the carbon-depleted surface layer in order to obtain a nitrided low-alloy steel part, step c) being performed after step b).

2. A method according to claim 1 , wherein the depth of the carbon-depleted surface layer lies in the range of 0.3 mm to 1.5 mm.

3. A method according to claim 1 , wherein, prior to step c), a step is performed of machining the carbon-depleted surface layer.

4. A method according to claim 1 , wherein, after step c), a step is performed of machining the nitrided layer formed during step c).

5. A method according to claim 1 , wherein the treated low-alloy steel part is made of 32CrMoV13 steel.

Assignees

• Messier Bugatti Dowty

Inventors

• Viola Alain
• Binot Nicolas

Classifications

• C21D1/25

  Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten") · CPC title

• C21D6/002

  containing Cr (C21D6/004 takes precedence) · CPC title

• C23C8/02

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

• C23F17/00

  Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25 (coating for obtaining at least two superposed coatings either by methods not provided for in a single one of main groups C23C2/00 - C23C26/00, or by combinations of methods providedfor in subclasses C23C and C25D, C23C28/00) · CPC title

• C22C38/22

  with molybdenum or tungsten · CPC title