KR100432966B1 - Heat-treatment method for improving the wear-resistance of overlay-welded nickel alloy layer - Google Patents

Abstract

The present invention is a heat treatment method for improving the wear resistance of the nickel alloy growth welding layer formed on the base metal by the plasma powder growth welding (PTAW) method to improve the wear resistance of the base metal.

To this end, the present invention provides a heat treatment method for improving the wear resistance of the nickel alloy growth welding layer, characterized in that the heat treatment at 760 ℃ for a time applied according to the thickness of the nickel-based alloy layer is welded on the base metal base material. Provide,

In addition, the heat treatment time applied according to the thickness of the nickel-based alloy layer to be welded provides a heat treatment method for improving the wear resistance of the nickel alloy growth welding layer, characterized in that 1 hour per 3mm thickness of the nickel-based alloy layer. .

As described above, the present invention has the effect of obtaining a growth layer having excellent wear characteristics by laminating a nickel-based growth welding layer on a base material by a plasma powder growth welding method and performing heat treatment at a temperature of 760 ° C. according to the thickness of the growth welding layer. There is.

Description

Heat Treatment Method for Improving Wear Resistance of Nickel Alloy Growth Weld Layer {HEAT-TREATMENT METHOD FOR IMPROVING THE WEAR-RESISTANCE OF OVERLAY-WELDED NICKEL ALLOY LAYER}

The present invention relates to a heat treatment method for improving the wear resistance of the nickel alloy growth welding layer according to the present invention, more specifically, the base metal by plasma powder growth welding (PTAW) method for improving the wear resistance of the base metal It is a heat treatment method for improving the wear resistance of the nickel alloy growth welding layer formed on the.

Wear or damage due to the wear, impact or erosion of equipment or mechanical parts, or corrosion due to the environmental effects will cause a lot of losses. In order to reduce this loss, the welding of abrasion resistant or corrosion resistant material on the surface of the material is called hardfacing or overlay welding. The application of wet welding to improve wear resistance ranges from very abrasive grinding such as rock grinding to contact wear between metals such as micro control valves that are not allowed to wear hundreds of millimeters. Corrosion and high temperature oxidation have a significant effect on the wear rate, which is a very important factor in the selection of materials for overlay welding. Typical installations are made of carbon steel, stainless steel or materials that lack wear resistance. Therefore, overlay welding is applied where the parts themselves are subject to severe wear or where the damaged parts are repaired.

The mechanical equipment is the most productive when the original machining dimension is maintained, and the quality of the product is excellent. Overlay welding maintains this useful dimension to the maximum, improving product quality, reducing maintenance cycles, and allowing expensive parts to be regenerated at low cost. In particular, it is possible to reduce the storage of parts and to reasonably manage spare storage parts, which can greatly contribute to the reduction of production cost.The above-mentioned welding welding has a thickness of about 1 mm or more on the base material, which is excellent in wear resistance, corrosion resistance, and heat resistance. As a method of coating welding metal, its characteristic is full fusion with the base material, which has higher bonding strength than the base material, and because of the high welding speed, the work efficiency is good and the thickness of the welding layer is easily controlled. Since the metallurgical reaction is performed in an inert gas atmosphere, the quality is excellent, and there is no limitation on the size of the product to be welded.

On the other hand, the economic advantage is to reduce the downtime for repair can be improved productivity, efficiency is increased even when using a slightly higher load, and repair and damage to reduce the maintenance, maintenance costs. In addition, wear and toughness are complementary due to the use of a tough and inexpensive base material.

The growth welding method having the above-mentioned advantages is classified into gas welding, arc welding, friction welding, and laser or electron beam surface modification. Among these, the conventional welding method is the arc development using electric arc and plasma arc. Welding methods are most commonly used.

The overlay welding by the arc dissolves and laminates the growth welding material on the surface of the material by using the heat of the electric arc discharge, and the arc is generated by applying a voltage between the electrode and the material. The voltage for holding the arc varies with the distance between the electrode and the material and also depends on the arc welding process. The welding material can be used as the electrode itself, but can be used separately from the electrode, and arc welding using the electrode as the welding material is called a consumable electrode type, and using the welding material separate from the electrode is a non-consumable electrode. It is called an expression. In general, non-consumable electrode type is less dilution degree and welding rate is lower than welding heat input type.

The consumable electrode arc welding method includes: sheathed metal arc welding (SMAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), submerged arc welding (Submerged Arc Welding (SAW)), and non-consumer arc welding method is Plasma Transferred Arc Welding (PTAW).

In the present invention, the powder is melted by a plasma heat source by the plasma powder growth welding (PTAW) method to form a growth layer by stacking the powder on the base material, and is performed to improve wear resistance and corrosion resistance of the base metal, which is mainly a base metal.

In the plasma powder growth welding method, as shown in FIG. 1, when the plasma arc 2 is generated between the tungsten (W) electrode 1 and the base material, the powder 3 is supplied between the plasma arcs and the plasma arc ( 2) The welded growth layer 5 is formed by laminating on the base material 4 while melting the powder 3 supplied by heat. At this time, argon protective gas (6) is supplied at the same time to prevent oxidation.

That is, in the plasma powder growth welding (PTAW) method, the powder is transferred to a plasma torch in an inert atmosphere and directly ejected into an arc to be dissolved and bonded to a base material to form a melt bond. Energy is supplied to the transition arc from the DC power supply connected between the electrode and the base material, and the supply of secondary current connected between the electrode and the nozzle maintains the non-transferred arc and is transferred. Arc) supplements the heat and serves as a guide when a transition arc occurs, and this plasma powder growth welding method uses an overlay welding layer with a width of 5 to 38 mm depending on the welding current, powder feed rate, vibration, and torch feed rate. It can be adjusted widely to 0.2-6 mm.

The alloy powder used as the material for the growth welding layer is classified into steel or Fe-based low alloy, Cr white iron or Fe-based high alloy, carbide, Ni-based alloy and Co-based alloy. It is composed of precipitates of high hardness, such as borides, carbides or intermetallic compounds, in a matrix of Ni, Co, and Co-based structures.

When the nickel (Ni) -based alloy is welded by using the plasma growth welding method, wear characteristics due to sliding contact between the metal and the metal are important. In the growth welding of the nickel-based alloy, the growth layer has a resin structure (Dendrite). However, because welding has a fast cooling rate, the structure is not uniformly formed by segregation of alloying elements in the central part of the dendritic phase and the dendritic and dendritic boundaries. Therefore, there is a problem that the sliding wear characteristics of the metal and the metal worsens.

As a conventional method for solving the above problems, as disclosed in US Pat. No. 5,624,717, the plasma powder growth welding method melts a portion of the base material because the powder is melted and laminated on the base material. A method of suppressing particle growth in the molten region by controlling it is proposed.

However, the method of improving the mechanical properties of the growth welding layer by controlling the conventional grain growth as described above is performed at the same time as the welding process, so that the control method requires a considerable skill and at the same time has a difficulty in technology.

In order to solve the above problems, the present invention is a nickel alloy growth welding layer which can improve the hardness and wear resistance of the growth welding layer by heat-treating the furnace for an applied time according to the thickness of the nickel-based alloy layer grown and welded on the base material. It provides a heat treatment method for improving the wear resistance of the.

1 is an operational state diagram showing the principle of the plasma powder growth welding method;

Figure 2 is a comparative graph showing the hardness change of the weld layer heat-treated according to the heat treatment method for improving the wear resistance of the nickel alloy growth welding layer according to the present invention;

Figure 3 is a comparative graph showing the wear rate of the weld layer heat-treated according to the heat treatment method for improving the wear resistance of the nickel alloy growth welding layer according to the present invention.

♣ Explanation of symbols for main part of drawing ♣

1: Tungsten electrode 2: Plasma arc 3: Welding powder 4: Base material 5: Growth layer

6: Protective gas 7: Plasma gas

In order to achieve the above object, the present invention is heat treatment for improving the wear resistance of the nickel alloy growth welding layer, characterized in that the heat treatment at 760 ℃ for a time applied according to the thickness of the nickel-based alloy layer grown and welded on the base material. Provide a method.

In addition, the present invention is a heat treatment for improving the wear resistance of the nickel alloy growth welding layer, characterized in that the heat treatment time applied according to the thickness of the nickel-based alloy layer to be welded is 1 hour per 3mm thickness of the copper nickel-based alloy layer. It provides a way.

Hereinafter, the present invention will be described in detail with reference to the embodiments of the present invention and the accompanying drawings.

EXAMPLE

Nimonic 80A, a nickel-based alloy, was used as the base material in the plasma powder growth welding method. In addition, the growth powder was nickel-based alloy Inconel 625, Table 1 shows the chemical composition of Nimonic 80A and Inconel 625.

In order to fabricate the hardness and wear characteristics test specimens after heat treatment of Inconel 625 layer, Nimonic 80A disk with diameter of 90mm / thickness of 15mm was welded with a thickness of about 3mm. The welding conditions are shown in Table 2. .

The specimens thus prepared were heat treated at 540 ° C., 760 ° C., 870 ° C., and 980 ° C. for 1 hour, and the hardness thereof was measured. The time applied at each temperature was determined according to the thickness of the nickel-based alloy layer welded on the base material. In the present invention, since the thickness of the growth welding layer is 3 mm, the welding layer is sufficiently heated and heat-treated if maintained at each temperature for 1 hour.

Therefore, when the thickness of the weld layer is formed thicker, the heat treatment time also increases in proportion thereto. When the thickness of the weld layer is formed thinner, heat treatment is performed by applying a reduced heat treatment time in proportion thereto.

In addition, wear specimens were prepared for the wear test of each of the specimens heat-treated as described above, and the wear specimens were made of cylindrical specimens having a diameter of 8 mm / 15 mm in length by electric discharge machining.

Figure 2 is a comparative graph showing the change in hardness of the weld layer heat-treated according to the heat treatment method for improving the wear resistance of the nickel alloy growth welding layer according to the present invention.

As shown in FIG. 2, the hardness after the welding was similar to that of the heat treated at 540 ° C. at about 205 Hv, and the hardness of the heat treated at 760 ° C. showed the highest hardness, 240 Hv. .

The abrasion test was carried out by the method specified in ASTM G99-95A, which is the most widely used sliding test method. At this time, abrasion test was performed at a sliding speed of 0.6 m / s with a load of 1.5 MPa. An alloy was used.

Figure 3 is a comparative graph showing the wear rate of the weld layer heat-treated according to the heat treatment method for improving the wear resistance of the nickel alloy growth welding layer according to the present invention.

As shown in Figure 3, the x-axis shows the heat treatment temperature conditions, the y-axis is a diagram showing the weight loss generated during the abrasion test is evaluated that the less the weight loss, the better the wear characteristics. Therefore, the wear characteristics have a lot to do with the hardness, so when the heat treatment at 540 ℃ the hardness value is similar to that of the non-heat-treated growth weld layer did not perform the wear test.

As can be seen in Figure 3, when the heat treatment at 760 ℃ shows the lowest weight loss shows better wear characteristics than the growth welding layer not heat-treated, when the heat treatment at the rest of the temperature does not heat up It can be seen that the wear characteristics are deteriorated rather than the weld layer.

The present invention has an effect of obtaining a growth layer having excellent wear characteristics by laminating a nickel-based growth welding layer on a base material by a plasma powder growth welding method and performing heat treatment at a temperature of 760 ° C. according to the thickness of the growth welding layer.

Claims (2)

delete A method for improving the wear resistance of a nickel-based alloy grown and welded on a base material by a plasma powder growth welding method, wherein the furnace is heat-treated at 760 ° C. for 1 hour per 3 mm of thickness of the nickel-based alloy layer welded on the base material. Heat treatment method for improving the wear resistance of the nickel alloy growth welding layer characterized in that.