JPS5823454B2 - Wear resistant alloy - Google Patents

Description

[Detailed Description of the Invention] The present invention is applicable to the face part of a valve of a nuclear power plant,
Concerning wear-resistant alloys suitable for jet pump parts, erosion shields for final stage blades in turbine low-pressure sections, control rod sliding parts, etc. As is well known, boiling water nuclear power plants use steam generated in nuclear reactors. This is a system that rotates a turbine and generates electricity.

However, in this power generation plant, water is vaporized in the nuclear reactor and sent to the turbine, which turns it into highly humid steam, which turns it into water in the condenser, and then is heated in the feedwater heater and sent to the reactor. It's a cycle that goes back and forth.

By the way, in this power generation system, corrosion products from various pipes used in the main steam pipe, condenser, feed water heater, etc., turbine blades, casing, etc., circulate and accumulate in the reactor, and neutrons emitted from the fuel rods are generated. It becomes radioactive and becomes a radioactive corrosion product.

Therefore, in this type of power plant, it is necessary to construct the valve face parts, which are subject to significant wear due to erosion caused by high-speed steam flow and cavitation erosion, and the erosion shields of the final stage blades of the turbine low-pressure section, from materials that can withstand wear and tear, and cobalt is usually used. Stellite containing about 50% is used.

Thus, during the aforementioned steam circulation, cobalt-59 in the constituent materials was brought into the reactor due to corrosion and loss.
There will be radioactive corrosion products containing cobalt-60 and other nuclides produced by the γ reaction.

However, the amount of radiation emitted from the radioactive corrosion products of the lever increases with the operating time of the power plant.

Therefore, when performing periodic inspections and repairs of power plants, it is necessary to take a long period of outage in order to wait for the radiation dose due to the radioactive corrosion products to be reduced.

The present inventors have carried out studies in view of the above points, and have found that certain types of chromium-niobium-nickel or chromium-niobium-molybdenum-nickel alloys have the wear resistance required as components for the above-mentioned power generation plants. I found out that I was prepared.

The present invention is based on the above findings, and is suitable for constituent materials such as the face parts of various valves in boiling water nuclear power plants, parts of jet pumps, erosion shields of final stage blades of turbine low pressure parts, and control rod sliding parts. The aim is to provide a wear-resistant alloy.

In detail, the present invention will be described below. The wear-resistant alloy of the present invention is characterized by having a composition, by weight, of 10 to 45% chromium, 3 to 15% niobium, and the balance containing nickel or less than 20% molybdenum. It is something.

As mentioned above, the wear-resistant alloy of the present invention is a chromium-niobium-nickel system or a chromium-niobium-molybdenum-nickel system containing Mo, and its composition ratio is 10 to 45% by weight of chromium, 3 to 15% by weight of niobium, and nickel. It is necessary to select a balance of 10 to 45% by weight of chromium, 3 to 15% by weight of niobium, 20% by weight or less of molybdenum, and a balance of nickel, and the reason for this is as follows.

First of all, chromium is a necessary component to strengthen corrosion resistance and the matrix of the alloy.If the composition ratio is less than 10%, the effect will be insufficient, and if it exceeds 45%, coarse primary α phase will precipitate excessively. Abrasion resistance cannot be obtained.

On the other hand, niobium is a component that reacts with nickel and contributes to strengthening the alloy base and improving wear resistance, but if the amount is less than 3%, the effect is insufficient, and if it exceeds 15%, the toughness may decrease. This is because the mechanical strength of the material is impaired.

Furthermore, molybdenum contributes to improving corrosion resistance, strengthening the alloy matrix, and improving wear resistance, but if it exceeds 20%, the toughness of the alloy decreases.

In addition, it is preferable that the alloy composition of the wear-resistant alloy according to the present invention is appropriately selected depending on the processing method and intended use.

For example, when forming by casting or overlaying, chromium 1
5-45%, niobium 7-15%, nickel balance or chromium 15-45%, niobium 7-15%, molybdenum 1
An alloy system with a balance of 0 to 20 nickel is desirable.

In addition, when forming by forging, chromium 10 to 40
%, 3 to 10% niobium, 3 to 10% niobium, balance of nickel or 10 to 40% of chromium, 3 to 10% of niobium, 10% or less of molybdenum, and the balance of nickel.

In the wear-resistant alloy according to the present invention, a portion of niobium may be replaced with aluminum, titanium, or tantalum.

Further, a part of nickel can be replaced with iron, and a part of Mo can also be replaced with W.

Furthermore, it may contain manganese, silicon, or the like as a deoxidizing and denitrifying agent that is added during melting.

Next, examples of the present invention will be described.

First, alloys having the compositions (% by weight) shown in Table 1 were prepared, melted and cast using a high frequency vacuum induction melting furnace, and then heat treated.

Next, a test piece was cut out from this cast product and a characteristic evaluation test was conducted.

This characteristic evaluation test was a cavitation erosion test using an ultrasonic vibration method, and was carried out for 3 hours in accordance with the Japan Science and Technology Act.

The results are also shown in Table 1. In addition, the amount of wear in Table 1 is the amount of weight loss of the test piece due to the test (772!i+)
is divided by the test time (minutes) and the density (gΔd) by 1×
It is multiplied by 106 and indicates the amount of volume reduction per hour.

Table 1 shows 1% chromium-1% molybdenum 0 for comparison.
．． 25% vanadium steel (Comparative Example 4), 18 chromium-8 nickel stainless steel (Comparative Example 5) or 12% chromium-
1% molybdenum-0.2% vanadinadium steel (Comparative example 6
) etc. 6 In the above table, the heat treatment conditions and symbols have the following relationship.

a...1200℃X2H→Water cooling 800℃X2H
b...1200℃X2H→Water cooling 800℃XIH
C...1200℃X2H→Water cooling 800℃×10
Hd・・・1200℃×2H→Water cooling 800℃×2
0He・・・1050℃X2H→oil cooling 650℃X
5Hf...1100℃X2H→Water cooling g...1100℃X2H→Oil cooling 650℃X5H
In addition, evaluation tests similar to those described above were conducted on test pieces cut out after forging alloys having the compositions (% by weight) shown in Table 2.

The results are also shown in Table-2.

Furthermore, an alloy having the composition (wt%) shown in Table 3 was added to 18Cr-
After overlay welding was performed on a 18Ni stainless steel plate, a test piece was cut out, and an evaluation test was conducted on the overlay welded surface in the same manner as described above.

The results are also shown in Table-3.

As is clear from the above test results, the wear-resistant alloy according to the present invention has less wear than the comparative examples and does not contain cobal, making it suitable as a constituent material for boiling water nuclear power plants. It can be said that it is a thing.

Claims (1)

[Claims] 1. Chromium 10-45%, niobium 3-15% by weight,
A wear-resistant alloy characterized by consisting of the remainder nickel. 2. A wear-resistant alloy comprising, by weight, 10 to 45% chromium, 13 to 15% nitro, 20% or less molybdenum, and the balance nickel.