JP2005187834A - MACHINE MEMBER HAVING NITROGEN-CONTAINING CrAl FILM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machine member having a hard film which includes SUJ2 steel, low carbon steel or medium carbon steel as a base metal, and in which the film hardness, adhesion and friction coefficient of the surface layer in the base metal are improved without worsening the functions of the material. <P>SOLUTION: The machine member having a nitrogen-containing CrAl film is obtained by forming at least one layer of nitrogen-containing CrAlN film having a composition of CrxAlyNz (wherein, x, y and z denote the elemental ratios of Cr, Al and N, respectively, and 0.01≤x≤0.99, 0.01≤y≤0.99, and 0.5≤z≤2.0 are satisfied) on the surface of a machine member including SUJ2 steel, low carbon steel or medium carbon steel as a base metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a machine member including SUJ2 steel, low carbon steel or medium carbon steel as a base material and having a nitrogen-containing CrAl coating.

  In many machine industries such as automobiles, the surface layer of materials used for machine parts containing SUJ2 steel, low carbon steel or medium carbon steel as a base material depends on the use of the machine parts. Various characteristics such as slidability, corrosion resistance, seizure resistance, and decorativeness are required, and are determined in consideration of the workability, productivity, economy, and the like of the member. For this reason, examples of materials used for machine members generally include SUJ2 steel, low carbon steel, or medium carbon steel, but in order to add the above characteristics to the surface layer, various heat treatments and carburization, Techniques have been developed that satisfy the desired characteristics by surface modification tailored to applications such as nitriding, and by forming functional coatings such as painting, vapor deposition, welding, chemical vapor deposition, and physical vapor deposition. One of the most commonly used surface treatment techniques is wet plating including hard chrome plating. This can improve the surface hardness to about Hv1000 to 1100, and can improve functions such as corrosion resistance, release, and slidability, and is used as an inexpensive processing method.

However, the treatment of harmful substances such as hexavalent chromium contained in the treated wastewater has become a problem, and an alternative technology is demanded in recent years due to environmental considerations that are increasing worldwide. In addition, companies have been actively engaged in environmental issues such as ISO14000, and the transition from wet plating to dry plating is progressing. Physical vapor deposition (PVD) Application of Cr vapor deposition by Physical Vapor Deposition) and nitrogen-containing Cr coating by physical vapor deposition method has been tried, but the former is not expected to improve the hardness sufficiently, and the latter has a high processing temperature of 400 ° C or higher Therefore, its application range was limited.
In order to cope with these problems, surface treatment of mechanical members with a nitrogen-containing Cr coating as disclosed in Patent Document 1 using a sputtering technique that is one of PVD methods has been proposed. However, low-grade steel such as SUJ2 (bearing steel) caused a decrease in the hardness of the base metal, and therefore a lower temperature treatment was required.
Summary of JP-A-11-217666

  The subject of the present invention was made in view of such circumstances, and without reducing the function of the material of the mechanical member including SUJ2 steel, low carbon steel or medium carbon steel as the base material. An object of the present invention is to provide a mechanical member having a hard coating with improved surface hardness, adhesion, and coefficient of friction.

  Therefore, in the present invention, CrxAlyNz, where x, y, and z represent the element ratio of Cr, Al, and N, respectively, on the surface of a mechanical member including SUJ2 steel, low carbon steel, or medium carbon steel as a base material, and 0.01 ≦ x The above-mentioned problems have been solved by a mechanical member having a nitrogen-containing CrAl coating characterized by forming at least one nitrogen-containing CrAlN coating having a composition of ≦ 0.99, 0.01 ≦ y ≦ 0.99, 0.5 ≦ z ≦ 2.0.

  Since the present invention described above has a nitrogen-containing CrAl coating containing aluminum with high heat dissipation characteristics, the surface layer of the base material is not reduced without deteriorating the function of the mechanical member including SUJ2 steel, low carbon steel or medium carbon steel as the base material. The present invention provides a mechanical member having a nitrogen-containing CrAl coating with improved film hardness, adhesion, and coefficient of friction.

Preferably, the nitrogen-containing CrAl film can be formed on the surface of the mechanical member by sputtering a combination of a plurality of chromium and aluminum targets, or a chromium aluminum alloy target having a controlled composition ratio in a nitrogen atmosphere.
More preferably, the nitrogen-containing CrAl coating can be formed on the surface of the machine member by performing a low-temperature treatment at 200 ° C. or less on the surface of the machine member.

  The best mode for carrying out the present invention is that CrxAlyNz, where x, y and z are the element ratios of Cr, Al and N, respectively, on the surface of a mechanical member containing SUJ2 steel, low carbon steel or medium carbon steel as a base material. A mechanical member having a nitrogen-containing CrAl film, wherein at least one nitrogen-containing CrAlN film having a composition of 0.01 ≦ x ≦ 0.99, 0.01 ≦ y ≦ 0.99, and 0.5 ≦ z ≦ 2.0 is formed. The nitrogen-containing CrAl coating according to the present invention was prepared by a magnetron sputtering apparatus shown in FIG. After a mechanical member containing SUJ2 steel, low carbon steel or medium carbon steel as a base material (not shown) is installed in the base material holder 2 in the vacuum vessel 1, it is evacuated and heated with a heater for degassing in the chamber. After raising the temperature to 0 ° C. and reaching a predetermined vacuum value, Ar gas is introduced and a constant pressure is maintained. The opposing two targets 4 and 4 are set to the minimum output for sustaining the discharge, the discharge is started, and the surface is cleaned by ion bombarding the mechanical member with Ar + ions generated by the sputter discharge. At this time, a negative potential of several hundred volts is applied to the mechanical member to accelerate Ar + ions and increase the bombard efficiency. Thereafter, in order to ensure the adhesion of the film, Cr is coated as a base film for a short time. Further, chromium and aluminum targets are set in advance on the pair of inclined magnetron sputtering cathodes, and the target output is adjusted so that the desired composition ratio is obtained in consideration of the sputtering yield of each raw material. The flow rate of N2 gas is adjusted so that the desired composition is obtained. Set the coating time in consideration of the required film thickness. As for the heater, heating is stopped after degassing and before the discharge of the magnetron cathode is started, thereby suppressing an increase in the substrate temperature. The sputtering targets 4 and 4 which are raw materials may be a combination of chromium and aluminum target materials alone, but may also be a chromium aluminum alloy whose composition ratio is adjusted.

  As is well known, aluminum has good heat dissipation characteristics, and by containing aluminum in the coating film, an increase in temperature can be suppressed. Figure 1 shows the temperature rise and cooling characteristics of the TiN and CrAlN coatings. This is a plot of changes over time in the surface temperature of a 1 mm thick SUS plate coated with a 2 μm TiN and CrAlN film, heated to the same amount of heat. The surface temperature was measured with a radiation thermometer. What should be noted at this time is the temperature rise at the initial stage of heating, and the CrAlN film containing Al shows a sharper temperature rise. This means that the Al-containing film has a faster heat flow rate, and from the opposite view, it means that the heat dissipation characteristics are high.

When a CrN film was formed by a conventional method using the sputtering apparatus shown in FIG. 2 and the treatment temperature was measured, it was 280 ° as shown in Table 1. Similarly, two types of CrAlN coatings with different aluminum contents were formed, and the treatment temperatures were measured and found to be 191 ° and 182 °. The inclusion of aluminum improves the heat dissipation characteristics of the CrAlN film as well during the formation of the film. In the sputtering apparatus shown in FIG. 2, the substrate to be coated is rotated to form a uniform film. When the substrate faces the sputter targets 4 and 4, the mechanical member is caused by thermal radiation from the plasma due to sputter discharge. The temperature is raised, but heat is released to the space or chamber furnace wall at a point away from the sputtering target surface. For this reason, as shown in Table 1, it was found that by mixing aluminum in the coating, the substrate temperature can be kept at 200 ° C. or lower and the temperature can be kept low by 30% or more compared with the formation of the CrN coating.

〔本発明の最良の実施形態の効果〕 Using the sputtering equipment shown in Fig. 2, Cr target output (KW): Al target output (KW) = 8: 6, nitrogen gas flow rate is introduced as appropriate, high speed steel (SKH57) so that the film thickness becomes about 2.0μm A film was formed. The composition ratio of the obtained film was measured by EPMA (Electron Probe Micro Analyzer), and the composition ratio was Cr: 0.46, Al: 0.12, and N: 0.42. The processing temperature was about 190 ° C. The film hardness was measured with a 50 g micro Vickers hardness meter, and the coefficient of friction was evaluated by a frictional wear test as shown in FIG. The film adhesion was evaluated using a scratch tester (not shown). Comparison was made with CrN and TiN coatings prepared at a processing temperature of 450 ° C. on the surface of high-speed steel (SKH57) by ion plating (not shown) (Table 2). As can be seen from Table 2, the surface of high-speed steel (SKH57) treated at a treatment temperature of 190 ° C. according to the present invention is CrN treated at 450 ° C. by ion plating in terms of film hardness, adhesion, and coefficient of friction. A nitrogen-containing CrAl film treated at a low temperature of 200 ° C or lower was realized on the surface of the machine member.

[Effect of Best Embodiment of the Present Invention]

  Since the above-described best embodiment of the present invention has a nitrogen-containing CrAl coating containing aluminum with high heat dissipation characteristics, the function of a mechanical member containing SUJ2 steel, low carbon steel or medium carbon steel as a base material is not deteriorated. Thus, the present invention provides a mechanical member having a nitrogen-containing CrAl coating with improved surface hardness of the base material, adhesion, and coefficient of friction.

Preferably, the nitrogen-containing CrAl film can be formed on the surface of the mechanical member by sputtering a combination of a plurality of chromium and aluminum targets, or a chromium aluminum alloy target having a controlled composition ratio in a nitrogen atmosphere.
More preferably, the nitrogen-containing CrAl coating can be formed on the surface of the machine member by performing a low-temperature treatment at 200 ° C. or less on the surface of the machine member.

The graph which shows the temperature rising and cooling characteristic of a TiN film and a CrAlN film. The schematic block diagram of the magnetron sputtering device used for the mechanical member of the best embodiment of this invention. 1 is a schematic block diagram of a friction wear test apparatus.

Explanation of symbols

1 Vacuum container (deposition chamber)
2 Base material holder 3 Target electrode 4 Target material 5 Electromagnetic coil
a Deposition zone
b Cooling zone

Claims (3)

On the surface of machine parts including SUJ2 steel, low carbon steel or medium carbon steel as a base material,
CrxAlyNz, where x, y, and z are elemental ratios of Cr, Al, and N, respectively, and at least one nitrogen-containing CrAlN film having a composition of 0.01 ≤ x ≤ 0.99, 0.01 ≤ y ≤ 0.99, and 0.5 ≤ z ≤ 2.0 is formed. A mechanical member having a nitrogen-containing CrAl coating characterized by the above. The nitrogen-containing CrAl coating is formed on the surface of the mechanical member by sputtering a chromium-aluminum alloy target in which a combination of a plurality of chromium and aluminum targets or the composition ratio is controlled in a nitrogen atmosphere. A mechanical member having the nitrogen-containing CrAl coating according to 1. The mechanical member having a nitrogen-containing CrAl coating according to claim 2, wherein the nitrogen-containing CrAl coating is formed on the surface of the mechanical member by performing a low temperature treatment at 200 ° C or lower.

Images