KR100361743B1 - Composite material for plasma transferred arc welding and method for plasma transferred arc welding the composite material - Google Patents

Abstract

PURPOSE: A composite material for plasma transferred arc welding that is applied to plasma hardfacing in which powder is melted using high density heat source of plasma to improve wear resistance and corrosion resistance of the surface of powder, and a method for plasma transferred arc welding the composite material are provided. CONSTITUTION: The composite material for plasma transferred arc welding is characterized in that a cobalt based matrix composition comprising 32.5 to 41 wt.% of cobalt (Co), 0.5 to 1.0 wt.% of carbon (C), 15 to 20 wt.% of chromium (Cr), 2.0 to 3.0 wt.% of tungsten (W) and 35 to 50 wt.% of ceramic powder WC-Co are used when plasma transferred arc welding steel products or iron. The method for plasma transferred arc welding the composite material for plasma transferred arc welding is characterized in that preheating temperature is maintained to 300 to 500 deg.C to obtain hardfacing layer in which pores or cracks are not formed during plasma transferred arc welding, the heat temperature is maintained to 300 deg.C if a matrix composition comprises 35 wt.% of WC-Co, 1.0 wt.% of C, 20 wt.% of Cr, 3.0 wt.% of W and 41 wt.% of Co, and the preheating temperature is increased as ceramic friction is being increased so that the heat temperature is maintained to 400 deg.C if the matrix composition comprises 50 wt.% of WC-Co, 0.5 wt.% of C, 15 wt.% of Cr, 2.0 wt.% of W and 32.5 wt.% of Co.

Description

Plasma cultivation composite material and its growth method

The present invention relates to a plasma growth composite material and a method for growing the composite material, and in particular, to a plasma growth welding for melting powder using a high density heat source of plasma, to improve the high wear resistance and corrosion resistance of the surface will be.

Commonly used powder materials can be broadly classified into iron-based, cobalt-based, nickel-based, and composite materials. Depending on the conditions of use and economics, a suitable powder is selected and used. The composite material is a material used for surface hardening of very abrasion parts, and is a material for obtaining very good wear resistance by mixing a hard ceramic with alloy powders such as iron-based, nickel-based or cobalt-based alloys with excellent toughness.

At present, the most widely used composite material is a mixture of WC-Co or W ₂ C ceramic with a nickel-based alloy base as specified in US Pat. No. 49,23511 (1990). Can be obtained.

However, the above composites often contain cracks in surface growth, and US Pat. No. 4,44,429,291 (1983) specifies a technique for adding some Nb and Mo to reduce cracking.

For special purposes, NbC ceramic composite powders (AU 9454592, 1994) on iron bases and ZrC ceramic composite powders (JP 62136597, 1987) on stainless steel bases and VC ceramic composite powders (US 4650722) are specified.

Japanese Patent (JP 58179568, 1983) states that a powder obtained by mixing ceramics of NbC, VC, and TiC on a copper or copper alloy base can be used to obtain an excellent surface growth layer using plasma growth welding.

In addition, Japanese Patent (JP 58179569, 1983) states that an excellent growth layer can be obtained as a composite material in which NbC, VC, and TiC ceramics are mixed with aluminum or aluminum alloy powder for surface growth of aluminum or aluminum alloy.

Although various techniques have been listed above, the most widely used commercially available composites containing WC-Co on nickel bases are the most widely used because of the inexpensive WC-Co powder compared to other ceramic materials. to be.

However, when the ceramic powder is used for the metal base as described above, wear resistance is improved, but corrosion resistance is generally decreased.

The object of the present invention is to add a suitable alloying element to the cobalt-based matrix to satisfy both abrasion resistance and corrosion resistance at the same time, and to use a powder mixed with an inexpensive WC-Co ceramic, and also excellent toughness compared to the nickel-based growth layer Less occurrence of cracking is to further suppress the occurrence of cracking phenomenon.

The characteristics of the present invention having the above object is that when the plasma growth of steel or iron, the known component is cobalt-based, cobalt 32-41%, carbon 0.5-1.0%, chromium 15-20%, and tungsten 2.0 A plasma growth composite material which improves abrasion resistance and corrosion resistance by growing a powder containing -3.0% and containing 35-50% of WC-Co, which is a ceramic powder;

Preheating temperature is 300-500 ℃, WC-Co is 300 ℃ at 35%, and the optimum preheating temperature is increased by increasing the ceramic fraction. In WC-Co of%, it is 400 degreeC.

1 is a powdery tissue photograph of the invention example 1

Figure 2 is a cross-sectional texture picture of Example 1 of the present invention

3 is a cross-sectional texture picture of Inventive Example 2

4 is a graph of corrosion test results of the present invention

WC is a ceramic powder containing 32-41% cobalt, 0.5-1.0% carbon, 15-20% chromium, and 2.0-3.0% tungsten. A plasma growth composite material for growing a powder containing 35-50% of Co to improve abrasion resistance and corrosion resistance;

Preheating temperature is 300-500 ℃, WC-Co is 300 ℃ at 35%, and the optimum preheating temperature is increased by increasing the ceramic fraction. In WC-Co of%, it was set as 400 degreeC.

Referring to the present invention configured as described above through the embodiment as follows.

Example 1

Plasma growing welding was made of masmododo, and the maximum output power of 200 A was used, and powder transfer gas, plasma gas, and protective gas were all used with argon.

As a base material, SS41 having a thickness of 15 mm was processed to 100 mm x 100 mm, and the plasma growth welding was performed.

As the powder material used, a material containing 35-80% of WC-Co's ceramic in a commercially available nickel-based matrix is shown in Table 1 below.

In the present invention, the powder contains 35-50% of WC-Co ceramic in a cobalt-based matrix. This is because when the ceramic content is 35% or less, the properties of the ceramic composite material become insignificant, the hardness decreases, and the wear characteristics remarkably decrease.

When the ceramic fraction is 50% or more, too much ceramic is contained, so that it is difficult to obtain good growth and the corrosion characteristics are also deteriorated. In Fig. 1, the powder form of Inventive Example 1 is shown. The spherical shape is a cobalt-based metal alloy, and the square shape is WC-Co ceramic.

Chromium was added to improve the corrosion resistance of the matrix and tungsten was added to give good strength properties at high temperatures.

Carbon was also added to form eutectic carbides with chromium to impart wear resistance to the matrix.

[Table 1] Component (weight fraction) of composite material used

Table 2 shows the surface hardness and the maximum hardness of the growth layer obtained using the powder of Table 1.

The obtained growth layer is a good growth layer in which no pores exist, and the thickness of the growth layer is about 2-3 mm.

[Table 2] Hardness Measurement Results of Plasma Growth Layer (Using Vickers Hardness 10kg)

When the surface hardness and the maximum hardness do not match in Table 2, the maximum hardness does not appear near the surface, and means a phenomenon appearing near the center of the growing layer.

Since the hardnesses shown in the invention examples are all almost similar to or higher than those in the prior art, it is expected that they will show similar or better wear characteristics.

Especially in the case of invention example 2, the known process carbide is added and the hardness is very high.

2 and 3 show cross-sectional texture photographs near the surfaces of Inventive Examples 1 and 2, respectively. In the picture, the square is a ceramic of WC-Co, and the base consists of a process structure showing cobalt and the last solidified lamellar shape. All have been shown to be good growth layers without pores and cracks.

Corrosion test was performed in 3% NaCl solution using the above grown layer. The corrosion tester used potentiostat to measure the initial corrosion current and corrosion potential.

The smaller the corrosion current, the slower the corrosion occurs. The smaller the absolute value of the corrosion potential, the less likely that corrosion occurs. Corrosion test results are shown in Figure 4, in the case of Inventive Example 1, both the corrosion potential and the current shows a significantly superior corrosion characteristics.

In the case of Inventive Example 2, the corrosion current is evaluated to be very excellent, but the corrosion voltage does not show a great improvement. Therefore, as the fraction of WC-Co ceramics increases, the wear characteristics increase but the corrosion characteristics decrease. In particular, in the ceramic fraction of 50% or more, it is difficult to obtain a good growth layer including many pores.

Example 2

Preheating temperature is required to obtain good growth, such as the tissue shown in FIGS. 2 and 3. However, if the preheating temperature is too high, the thermal stress with the base material is increased, and the warpage phenomenon of the base material is increased, so the present invention is limited to a maximum of 500 ° C.

Many cracks exist until the preheating temperature is 200 ° C., and in the case of Inventive Example 2, a pore frame exists. This disappearance could be observed.

As the preheating temperature increases, the thermal stress with the base metal increases and the warpage of the base material increases, so the optimum preheating temperature is 300 ° C. in the case of Inventive Example 1 containing 35% of ceramic, and as the ceramic fraction increases. When the preheating temperature is increased to contain 50% of the ceramics of invention example 2, 400 ° C is evaluated as the most suitable preheating temperature.

[Table 3] Structure Observation Results of Growth Layers According to Preheating Temperature

The present invention as described above can obtain excellent properties compared to the conventional, and excellent excellent high temperature characteristics can be obtained more excellent wear resistance at high temperatures, and the resulting growth layer also has excellent toughness as cobalt-based shows excellent toughness compared to nickel-based Will be carried.

In addition, cobalt has better resistance to Zn than nickel, and thus, when applied to various components in molten Zn, excellent properties can be obtained, and an excellent growth layer free of cracks and pores can be obtained.

Claims (2)

In the plasma growth of steel and iron, the known ingredients are cobalt-based, with cobalt containing 32.5-41%, carbon 0.5-1.0%, chromium 15-20%, and tungsten 2.0-3.0%, and the ceramic powder WC- A composite material for plasma growth, characterized by growing powder containing 35-50% of Co. Preheating temperature is set to 300-500 ℃, WC-Co is 35%, C is 1.0%, Cr is 20%, W is 3.0%, Co is 41% At 300 ℃, the preheating temperature increases with increasing ceramic fraction, resulting in WC-Co of 50%, C of 0.5%, Cr of 15%, W of 2.0% and Co of 32.5% at 400 ℃. Method for growing composite material for plasma growth.