JP2008115444A - HEAT RESISTANT Cr-BASED ALLOY HAVING HIGH HARDNESS FOR SURFACE HARDENING - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat resistant Cr-based alloy having high hardness for surface hardening which has excellent corrosion resistance and heat resistance, and whose hardness is increased for improving its wear resistance. <P>SOLUTION: The heat resistant Cr-based alloy having high hardness for surface hardening has a composition comprising, by weight, 20 to 40% Ni, 2.5 to 7.0% Si, 0.5 to 8.0% W or/and 1.0 to 6.0% Mo, 0.1 to 1.5% B, and the balance Cr including inevitable impurities of 55 to 65%, and in which the total of W and Mo is ≤8.0%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface-hardened material having excellent wear resistance, corrosion resistance, and heat resistance, which is used in various construction processes such as various types of overlay welding, thermal spraying, and powder metallurgy, and particularly requires wear resistance. The present invention relates to a high-hardness, heat-resistant Cr-based alloy for surface hardening that is effective for parts.

  Conventionally, Co-Cr-W alloys and Ni-Cr-B-Si self-fluxing alloys have been widely used as surface hardened materials with wear resistance and corrosion resistance, but wear resistance, corrosion resistance, heat resistance It is hard to say that they have all.

  Further, a high toughness chromium-based alloy for hard facing is an alloy having excellent toughness, corrosion resistance, and wear resistance, but is not sufficient in terms of wear resistance, that is, hardness, and may not satisfy customer requirements ( Patent Document 1).

Japanese Patent No. 3148340

  The present invention pays attention to the above-mentioned problems, and for the purpose of finding an alloy composition having excellent corrosion resistance and heat resistance and having increased hardness in order to further improve wear resistance (Patent Document 1). The issue was to review the ingredients of the plant and restructure its balance.

  In order to review the components of (Patent Document 1) and develop the alloy of the present invention, the following target values were set, and all of these were satisfied.

(Target value)
・ Hardness (guideline for high hardness); 55HRC or more ・ Solidus temperature (guideline for high temperature); 1100 ° C or more By weight% (hereinafter referred to as%) Ni 20-40%, Si 2.5-7.0%, W 0.5-8.0% or / and Mo 1.0-6. A surface comprising 0%, 0.1% to 1.5% B, the remaining Cr content of unavoidable impurities is 55% to 65%, and the total of W and Mo is 8.0% or less High hardness heat resistant Cr-based alloy for hardening.

  In addition, the inevitable impurities include Fe 3% or less, Co 1% or less, Cu 1% or less, Mn 1% or less, and C 0.1% or less. Hard heat resistant Cr-based alloy.

  Next, the reason why the respective component ranges of the alloy of the present invention are limited will be described.

  The alloy of the present invention is basically formed of “Cr solid solution” and “Ni solid solution”, and is designed on the Cr rich side to improve hardness and heat resistance while maintaining excellent corrosion resistance.

Ni, as well as Cr, is a component that is the base of the alloy of the present invention, and combines with Si to form an intermetallic compound such as Ni ₃ Si to increase the hardness. If the phase line temperature rises to an unfavorable temperature and exceeds 40%, the Cr amount inevitably decreases and the hardness decreases. For this reason, Ni was limited to the range of 20 to 40%.

  In the alloy of the present invention, Si is a component that exhibits a particularly important effect in adjusting the increase in hardness and the melting point (liquidus and solidus temperature), and it is important to limit the amount of addition.

Si is mainly contained in Ni solid solution and forms intermetallic compounds such as Ni ₃ Si and also bonds with Cr to form intermetallic compounds such as Cr ₃ Si, which is effective in increasing the hardness of the alloy. However, if it is less than 2.5%, the target hardness cannot be obtained, and if it exceeds 7.0%, the alloy becomes brittle and cannot be used. For this reason, Si was limited to 2.5 to 7.0%.

  W and Mo increase the hardness of the alloy by solid solution in Cr and Ni, and are effective in improving corrosion resistance and high temperature characteristics, and can be added individually or in combination. If W is less than 0.5% and Mo is less than 1%, there is no effect. If W exceeds 8.0%, Mo exceeds 6.0%, and the total of both exceeds 8.0%, the liquid phase of the alloy The wire temperature rises to an undesirable temperature and the alloy becomes brittle. For this reason, W is limited to 0.5 to 8.0% or / and Mo is limited to 1.0 to 6.0%, and the total of both is limited to 8.0% or less.

B combines with Cr to form an intermetallic compound such as Cr ₂ B, and has the effect of increasing the hardness of the alloy and adjusting the melting point, but less than 0.1%, this effect is not exhibited, If it exceeds 1.5%, the alloy becomes brittle. For this reason, B was limited to the range of 0.1 to 1.5%.

  Cr is a basic component that exhibits the effect of increasing the heat resistance, corrosion resistance, and hardness of the alloy of the present invention, but the Cr amount including inevitable impurities is in the range of 55 to 65% due to the balance with each of the above components. It is limited to.

  The range of impurities that do not adversely affect the properties of the alloy of the present invention is as follows: Fe 3% or less, Co 1% or less, Cu 1% or less, Mn 1% or less, C 0.1% or less And limited.

The high-hardness heat-resistant Cr-based alloy for surface hardening according to the present invention has the following characteristics and can be applied to a wide range of applications.
・ Hardness is as high as 55HRC or more, especially excellent wear resistance.
-The solidus temperature is as high as 1100 ° C or higher, and the heat resistance is good.
・ Maintains excellent corrosion resistance.

  Base metal adjusted and blended so that each of Cr, the additive component, and Ni, Si, W, Mo, and B as the specified weight% is heated and melted in a crucible in a melting furnace to form a liquid alloy. After that, the alloy of the present invention can be obtained in the form of a rod or plate by powdering by an atomizing method or casting into a predetermined mold.

  In particular, the alloy powder produced by the atomizing method is effective because it can be applied to surface hardening materials such as overlay welding and thermal spraying, powder metallurgy materials, etc. by adjusting the particle size to be suitable for the intended construction method.

  The example alloy and comparative example alloy of the present invention prepared and blended as described above were melted, and the hardness and melting point (liquidus temperature, solidus temperature) were measured by the following methods.

  (1) Hardness: 100 g of ingot having a composition composition of each alloy is heated and melted at about 1600 ° C. in an argon stream using a normal electric furnace, and cast into a shell mold to produce a rectangular parallelepiped test piece. After polishing both parallel surfaces, the hardness (HRC) of the alloy was measured with a Rockwell hardness meter.

  (2) Liquidus temperature, solidus temperature: Insert a thermocouple into the molten alloy melted in the same way as above, draw a cooling curve on the recorder, analyze the curve and analyze the alloy The liquidus temperature and the solidus temperature were measured.

  Table 1 shows examples of the present invention. Table 2 shows a comparative example.

  Comparative Examples 1 to 6 are alloys outside the scope of the present invention, Comparative Example 7 is a conventional Co—Cr—W alloy, and Comparative Example 8 is a Ni—Cr—B—Si self-fluxing alloy. In Comparative Examples 1, 2, and 3, Si is mainly below the lower limit of the claims, and the hardness does not satisfy the target value. In Comparative Example 4, Si exceeded the upper limit of the claim range, in Comparative Example 5, W exceeded the upper limit of the claim range, in Comparative Example 6, W + Mo and B exceeded the upper limit of the claim range, Ni charged Although both are below the lower limit of the range, not only the alloy is brittle and cracked, the hardness cannot be measured, but the solidus and / or liquidus temperature does not satisfy the target value. Conventional alloys Comparative Examples 7 and 8 have insufficient hardness.

  On the other hand, as is clear from Table 1, Examples 1 to 15 which are the alloys of the present invention satisfy the target values for hardness, solidus temperature and liquidus temperature. Further, the alloy of the present invention has been confirmed to have good corrosion resistance in various acids, and has high hardness, heat resistance, and corrosion resistance as a surface hardening material.

  As described above, the high hardness heat-resistant Cr-based alloy for surface hardening according to the present invention has a particularly high hardness, so that it can be effectively applied to parts that require higher wear resistance. In addition, since it has excellent corrosion resistance and heat resistance, it can be applied to a wide range of applications.

  The alloy of the present invention can be used in a wider range of applications by combining with various surface hardening processes such as overlay welding and thermal spraying.

  In addition, the alloy of the present invention is not limited to surface hardening, and sintered parts by powder metallurgy, for example, the powder of the alloy of the present invention is mixed and dispersed as hard particles in matrix powder, molded and sintered. It can also be applied to forming mechanical parts having corrosion resistance, heat resistance and wear resistance.

Claims (2)

  In weight% (hereinafter referred to as%), Ni is 20 to 40%, Si is 2.5 to 7.0%, W is 0.5 to 8.0%, and / or Mo is 1.0 to 6 0.0%, containing 0.1 to 1.5% of B, the remaining Cr containing unavoidable impurities is 55 to 65%, and the total of W and Mo is 8.0% or less High-hardness heat-resistant Cr-based alloy for surface hardening.   2. The surface hardening high according to claim 1, wherein the inevitable impurities include Fe of 3% or less, Co of 1% or less, Cu of 1% or less, Mn of 1% or less, and C of 0.1% or less. Hard heat resistant Cr-based alloy.