JPH0366379B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a Ni-based alloy, and particularly to a Ni-based alloy that can be subjected to boriding treatment. Furthermore, from another perspective, the present invention relates to a method of accelerating boriding treatment of a Ni-based alloy. (Prior Art) Various mechanical parts and tools are often required to have hardness and wear resistance, and research on materials is being conducted to meet these requirements. However, since hard and wear-resistant materials are generally difficult to process,
Research is also being conducted on forming a soft material into a predetermined shape and then subjecting it to surface hardening treatment after the processing. For example, special steel called nitriding steel is not hardened during the forming process, but is nitrided and surface hardened after processing to produce mechanical parts with improved wear resistance. It is also known that nitriding stainless steel significantly hardens its surface. This is because Cr and Al contained in nitriding steel and stainless steel become nitrides through nitriding treatment, forming a hard nitrided layer on the surface of the article. However, in the case of alloys whose main component is iron, such as nitriding steel and stainless steel, Cr in the alloy becomes nitrides and is lost, resulting in a significant decrease in the Cr concentration in the base metal directly below the nitride layer. Therefore, corrosion resistance deteriorates and iron rust is likely to occur. On the other hand, metallic Ni has much better corrosion resistance than Fe, and hardly corrodes in the atmosphere, freshwater, and seawater. In addition, it has relatively good workability and can be processed into shapes such as plates, rods, and wires. However, since metal Ni is extremely difficult to nitride, a nitride layer cannot be formed on the surface using normal methods. It is also known that metal Ni can produce a hardened layer containing boride on its surface by boriding, but its hardness is around Hv800, and if a surface with even higher hardness could be obtained. Needless to say, it has a remarkable effect on improving wear resistance. (Problems to be Solved by the Invention) The present inventors have discovered that metallic Ni can be processed into the shapes of plates, rods, and wires, and that it can be surface hardened by boriding treatment to obtain a hardness of Hv800 or higher. Focusing on
We have begun developing a Ni-based alloy that can obtain an extremely hard surface by boriding. (Means for solving the problem) Here, the present inventors have discovered that Ti, Nb, Si, Zr,
The present invention was completed based on the discovery that by adding an appropriate amount of at least one of Hf, Mo, and Ta, metal Ni becomes extremely hard when subjected to boriding treatment. Therefore, the gist of the present invention is that the weight %
So, Ti: 0.1~15%, Nb: 0.2~20%, Si: 0.2~10%, Zr: 0.05~5%, Hf: 0.05~5%, Mo: 0.25~25%, and Ta: 0.1~15. %, provided that one of them
When containing only seeds, the lower limits of content are Ti: 0.2%, Nb: 0.4%, Si: 0.4%, Zr:
0.1%, Hf: 0.1%, Mo: 0.5%, and Ta: 0.2
%, and the balance is essentially Ni, which is a Ni-based alloy for boriding. It is known that Ti, Nb, Si, Zr, Hf, Mo, and Ta form borides, but according to the present invention, since the matrix is Ni, the formation is not only significantly easier, but also Because the diffusion rate of boron is high, taking Ti as an example, when the matrix is Ni compared to when the matrix is Fe, hardly any diffusion of Ti occurs, and therefore even after boron treatment, the diffusion of Ti hardly occurs. A Ti-depleted layer is not formed directly under the compound layer. (Function) In the present invention, the reason why the amount of each additional element of Ni is numerically limited as described above is as follows. All of the above additive elements form borides through boriding treatment to promote surface hardening.
It has the effect of promoting the boronization of Ni and the diffusion of boron into the matrix, but additional properties will be improved for each of the other properties, and when determining the actual alloy composition, The degree of surface hardening and the effects of other property improvements are taken into consideration. In addition, in this specification, % is weight % unless otherwise specified. Zirconium (Zr), Hafnium (Hf): Zr and Hf are elements that make Ni-based alloys extremely susceptible to boronation. The effect tends to increase as the amount added increases, but when each amount exceeds 5%, the workability of the alloy deteriorates significantly. Furthermore, if the amount is less than 0.1% when added alone, or less than 0.05% when added in combination, the effect of addition is difficult to recognize. Preferably it is 0.5-3.0%. Titanium (Ti), tantalum (Ta): Ti and Ta function in the same way as Zr and Hf. When the amount of Ti and Ta added exceeds 15%, the workability deteriorates significantly, and when each is added alone at less than 0.2%, and when added in combination less than 0.1%, the desired effect cannot be obtained. Preferably each content is 1.0 to 10.0%. Niobium (Nb): Nb not only promotes boronization of Ni-based alloys and improves surface hardening, but also improves the corrosion resistance and strength of the base material. However, if Nb alone is less than 0.4% or if the combined addition is less than 0.2%, no effect will be observed, and if Nb exceeds 20%, workability will deteriorate. Preferably it is 2.0 to 15.0%. Silicon (Si): Si promotes surface hardening of Ni-based alloys by boriding and also works to improve the heat resistance of the base material. To obtain this effect, 0.4% or more alone,
More than 0.2% Si is required in composite addition;
Si exceeding 10% causes deterioration of workability.
Preferably it is 2.0 to 7.0%. Molybdenum (Mo): Mo has the effect of improving the boriding properties of Ni-based alloys and promoting surface hardening, as well as further improving corrosion resistance, but in order to fully demonstrate its effects, it must be used alone in an amount of 0.5% or more. With complex addition
It is necessary to add 0.25% or more of Mo. However, adding more than 25% Mo deteriorates workability and increases costs, so the upper limit was set at 25%. Preferably it is 3.0 to 20.0%. In the present invention, what is referred to as "for boration treatment" is
This means that the material is easily borated by the boron treatment, and not only does the surface become hard due to boronization, but also boron diffuses from the surface to the inside, and as a result, the hardness and strength of the material decreases. It also includes rising. Therefore, as an aspect of the present invention, the weight %
So, Ti: 0.1~15%, Nb: 0.2~20%, Si: 0.2~10%, Zr: 0.05~5%, Hf: 0.05~5%, Mo: 0.25~25%, and Ta: 0.1~15. %, provided that one of them
When containing only seeds, the lower limits of content are Ti: 0.2%, Nb: 0.4%, Si: 0.4%, Zr:
0.1%, Hf: 0.1%, Mo: 0.5%, and Ta: 0.2
%, with the remainder being essentially Ni, is formed into the shape of a predetermined article, and then boron is permeated and diffused from the surface of the Ni-based alloy. In addition, in the examples of the present invention, the "solid method" of heating together with boron powder is used as the method of boron treatment.
Although only exemplified above, the Ni-based alloy according to the present invention can be processed by the "molten salt bath method" using a boron-containing salt,
Needless to say, it is also easily borated by the "gas method" using BCl ₃ gas. This is because the boronization reaction is a reaction between alloy components and boron, and the rate of boron diffusion into the alloy is also unique to that alloy. This is because, regardless of the form in which it is supplied, it mostly depends on the properties specific to the alloy. Next, the present invention will be further explained by examples. Example An alloy having the composition shown in Table 1 was melted using a high-frequency induction heating vacuum melting method, forged into a plate with a thickness of 10 mm, heat-treated at 900° C. for 15 minutes, and air-cooled.
From this, a test piece with a thickness of 2 mm x length of 10 mm x width of 10 mm was cut out, embedded in amorphous boron powder in a graphite crucible, and boronated by heating at 950°C for 3 hours while flowing Ar gas. . After finishing the boriding process,
The graphite crucible was taken out of the heating furnace and cooled, and the test piece was taken out and cut, and the hardness of the boride layer was examined by measuring it using a micro-Vickers hardness meter at a load of 250 g. The maximum crack length for ear cracks is 5mm.
The following cases were evaluated as A, and cases where the maximum crack length was 10 mm or less were evaluated as B, and in both cases, there was no problem in practical use. Table 1 also shows the test results for the hardness of the borated layer. The alloys of the present invention (Nos. 1 to 18) containing at least one of Ti, Nb, Si, Zr, Hf, and Mo are compared to the comparative alloys (Nos. 19 to 20) that do not contain these alloying elements.
It was shown that the hardness of the borated layer was greater than that of the hardness of the borated layer. Comparative alloys with large amounts of added Ti, Nb, etc. (No. 21~
27) had extremely poor workability and could not be processed by forging, making it impossible to create test specimens for boriding treatment. Next, the above-described boriding treatment was repeated for each of the above-mentioned additive elements, and the relationship between the amount added and surface hardening was determined. The hardness of the boride layer increases as the amount of added elements increases, but the degree of hardness varies depending on the element, as shown in FIG. 1.

【table】

[Table] (Effects of the invention) As detailed above, the present invention provides a
According to the present invention, the following benefits can be obtained. (1) The good workability of Ni metal can be fully utilized, allowing it to be formed into pipes, wires, and even products with complex shapes, as well as applying treatments to improve wear resistance at the required locations on the product. can do. (2) By appropriately selecting the additive components of the above-mentioned article, it is possible to obtain an article that has a combination of excellent wear resistance and improved corrosion resistance or strength. (3) In the case of boron treatment, the diffusion rate of boron is fast, so the formation of a layer depleted of additive components on the surface is sufficiently prevented, and even if it is formed, the corrosion resistance is reduced by the base Ni metal. , high temperature strength is compensated. (4) Other possibilities include increasing strength and improving vibration characteristics.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of various alloying elements added to Ni and the hardness of the boride layer.

Claims (1)

[Claims] 1% by weight: Ti: 0.1~15%, Nb: 0.2~20%, Si: 0.2~10%, Zr: 0.05~5%, Hf: 0.05~5%, Mo: 0.25~ 25%, and Ta: 0.1 to 15%, provided that one of them
When containing only seeds, the lower limits of content are Ti: 0.2%, Nb: 0.4%, Si: 0.4%, Zr:
0.1%, Hf: 0.1%, Mo: 0.5%, and Ta: 0.2
%, with the remainder consisting essentially of Ni.