JPH04314821A - Method for surface hardening treatment - Google Patents

Abstract

PURPOSE:To form a surface treated layer having extremely high hardness on the surface of a steel by forming a hard film of metal or ceramics on the surface of a steel and thereafter executing nitriding treatment. CONSTITUTION:A steel 1 in which its surface has been cleaned is subjected to sputtering of Ti, Al, N or the like by thermal spraying, sputter ion planting (SIP), etc., to form a hard ceramic film 3 of TI-Al-N or the like. Because this hard film 3 is a porous one, ion nitriding treatment is executed, and N is infiltrated from a fine pore if the hard film 3 to form a nitride film 2 of Fe between the film 3 and the steel 1 and to improve the adhesion between the steel 1 and the hard film 3, by which the surface treated steel extremely high in surface hardness and excellent in durability can be manufactured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface hardening method.

0002

2. Description of the Related Art Conventionally, a surface hardening treatment method is known in which a steel material is plated or vapor-deposited and the surface is hardened with a hard metal or ceramic film.

0003

[Problems to be Solved by the Invention] However, steel materials that have been plated or vapor-deposited still have insufficient surface hardness in some cases. However, if a nitrided layer is provided on the surface of the steel material in advance to harden the surface of the steel material, and then plating or vapor deposition is applied to the surface of the nitrided layer, the adhesion of the hard metal or ceramic film caused by plating will be weak, resulting in poor wear resistance. Poor properties lead to poor durability.

The present invention has been made in view of the above-mentioned conventional problems, and provides a surface hardening treatment method that can increase the surface hardness compared to the conventional method while strongly adhering a hard film of metal or ceramics. The purpose is to

[0005]

[Means for Solving the Problems] The surface hardening treatment method of the present invention comprises a coating step of coating a steel material with a hard film of metal or ceramics, and a nitriding step of nitriding the steel material coated with the hard film. It is characterized by consisting of.

In the coating step, the steel material is coated with a hard metal or ceramic film. This coating process includes thermal spraying, CVD, vacuum deposition, ion plating, SIP
(sputter ion plating) etc. can be adopted. The metal or ceramic hard film preferably contains nitrogen from the viewpoint of improving surface hardness. As a coating process, TiAlN, T
It is preferable to apply a hard film such as iAl6V4CN or TiN from the viewpoint of improving surface hardness.

In the nitriding process, the steel coated with the hard film is nitrided. This nitriding process can be performed as an ion nitriding process by placing the steel material in a mixed gas of nitrogen and hydrogen under low pressure, applying a voltage using the steel material as a cathode, and causing the mixed gas to glow discharge. This is preferable in terms of improving surface hardness.

[0008]

[Operation] When a steel material is coated with a hard film of metal or ceramics, the hard film becomes porous. In the surface hardening treatment method of the present invention, since the nitriding treatment is performed after this,
It is thought that during the nitriding treatment, nitrogen acts on the steel material through the pores of the hard film, and the surface of the steel material is further hardened through the nitrided layer.

Furthermore, if the hard film coated on the steel material contains nitrogen, it is thought that the nitrogen during the nitriding treatment and the nitrogen in the hard film will diffuse into the steel material. Nitriding process is SI
If P treatment is used, nitrogen is considered to be more likely to diffuse. In this way, the adhesion of the hard film is stronger than if a nitrided layer is applied to the surface of the steel material in advance and then plated, etc.
And sufficient surface hardness can be obtained.

0010

[Examples] Examples embodying the present invention will be described below together with comparative examples with reference to the drawings. (Example) First, maraging steel was machined,
A steel material in the shape of a part for a urethane molding machine was prepared. and,
The steel material was subjected to age hardening treatment at 400 to 600°C for 3 hours to give a surface hardness of Hv (200 g) of 484 to 544. After this, the steel material was subjected to finish machining.

{Coating process} Applying S to the steel material after finish machining
IP treatment was performed. In other words, the steel material is 10-5mb
It is equipped in a vacuum container below ar, and 15
2 to 8 x 10-3m by introducing Ar gas at 0 to 250℃
The pressure was set at bar. Then, a DC electric field of 400 to 600 V is applied using the TiAlN target as a cathode and an anode to cause a glow discharge in the Ar gas, and the A
The r ions were ionized. These Ar ions clean the surface of the steel material, and the Ar ions also remove Ti, Al, and N ions from the target, and the surface of the steel material is coated with Ti, Al, and N ions.
l, N ions were attached. After this, the steel material was cooled. In this way, a hard film made of TiAlN with a thickness of 2 μm was applied. This hard film was porous.

{Nitriding process} Next, the steel coated with the hard film was subjected to ion nitriding. That is, the steel material is used as a cathode in a vacuum container with a pressure of 13 Pa or less, and a mixed gas of nitrogen:hydrogen = 1:1 (volume ratio) is introduced into the vacuum container at 400 to 480°C to a pressure of 133 to 266 Pa. And so. Then, a DC electric field of 400 to 500 V was applied to the anode to cause glow discharge in the mixed gas, thereby ionizing N ions from the mixed gas. The condition was maintained for 0.5-1.5 hours. After this, the steel material was cooled. In this way, a nitrided layer made of a compound of iron and nitrogen and having a thickness of 0.05 to 0.15 mm was formed between the hard film and the steel material.

A cross section of the treated steel material thus obtained is shown in FIG. In this treated steel material, a nitride layer 2 was formed on the surface side of the steel material 1, and a hard layer 3 was further formed on the surface side. (Comparative Example) Using the same type of steel as in the example, the coating process was carried out in the same manner as in the example. In this way, a 2 μm thick TiAl
A hard film made of N was applied. This hard film was porous.

FIG. 2 shows a cross section of the treated steel thus obtained. In this treated steel material, a hard layer 3 was formed on the surface side of the steel material 1. (Evaluation) The surface hardness of the treated steel material according to the example is Hv (
50g) 980-1000, Hv (200g) 850. On the other hand, the surface hardness of the treated steel material according to the comparative example is
Hv (50g) 960-1000, Hv (200g) 5
It was 70-590.

Therefore, it can be seen that the surface hardening method of the example improves the surface hardness by Hv (200 g) compared to the comparative example in which the nitriding process is not performed. That is, in the method of the embodiment, since the ion nitriding process is performed as a nitriding process after the coating process, N ions act on the steel material 1 through the pores of the hard film 3, and the surface of the steel material 1 is further damaged through the nitrided layer 2. It is thought that it has been hardened. Further, in the method of the embodiment, the hard film 3 coated on the steel material 1 is made of Ti containing nitrogen.
Since it is AlN, it is considered that nitrogen ions during the ion nitriding treatment and nitrogen in the hard film 3 were easily diffused into the steel material 1 by the SIP treatment.

[0016] This shows that the adhesion of the hard film 3 is stronger and a sufficient surface hardness can be obtained than when a nitride layer is previously applied to the surface of the steel material 1 and then plating or the like is applied.

[0017]

[Effects of the Invention] As detailed above, in the surface hardening treatment method of the present invention, the nitriding treatment is performed after coating the steel material with a metal or ceramic hard film. The surface hardness can be made higher than before while the adhesive remains attached to the surface.

[0018] Therefore, if the surface hardness of the steel material is improved by this surface hardening treatment method, the steel material will have excellent abrasion resistance and will be able to exhibit excellent durability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a treated steel material subjected to a surface hardening treatment method of an example.

FIG. 2 is a cross-sectional view of a treated steel material subjected to a surface hardening treatment method of a comparative example.

[Explanation of symbols]

1... Steel material 2... Nitrided layer
3...Hard membrane

Claims (1)

[Claims] 1. A surface hardening treatment method comprising: a coating step of coating a steel material with a metal or ceramic hard film; and a nitriding step of nitriding the steel material coated with the hard film.