JPH01127659A - Method for making sprayed deposit dense - Google Patents

Abstract

PURPOSE:To easily make a sprayed deposit dense and to improve quality by holding a deposited layer/based metal clad material in vacuum at a temp. in the solid-liquid coexisting temp. region of a thermal spraying material to melt the surface of a sprayed deposit, lowering the temp. down to a temp. of the solids temp. or below, and then applying hot isostatic pressing to the above sprayed deposit. CONSTITUTION:A clad material which sprayed deposit is formed on a base metal is held in a vacuum, desirably, of <=about 1X10<-1>Torr at a temp. in the solid-liquid coexisting temp. region of a thermal spraying material, preferably in the temp. region where liquid phase comprises <=about 10%, by which gases inside the micropores in the sprayed deposit are excluded and only the surface of the sprayed deposit is melted. Subsequently, the temp. of the clad material is lowered down to a temp. of the solids temp. of the thermal spraying material or below, by which the above micropores are sealed in a vacuum state. Then, this clad material is subjected, in the above state, to hot isostatic pressing so as to be made dense. By this method, the micropores in the sprayed deposit are removed and quality can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for densifying a thermally sprayed coating of a composite material on which a thermally sprayed coating has been formed and improving its quality.

(Prior Art) There is a composite material that has improved wear resistance, corrosion resistance, etc. by forming a thermal spray coating on the surface of a metal base material. Since the thermal spray coating has a large number of micropores, the thermal spray coating cannot fully exhibit its characteristics, and has the disadvantage that the strength of the coating decreases.

The fusing method and hot isostatic pressing (hereinafter referred to as HI) are methods for removing such defects and improving the quality of the sprayed coating.
It's called P. ) There is a law. The fusing method is a method in which a thermally sprayed coating is remelted using a heating means such as a gas burner, and defects in the coating are lifted or melted to remove the defects. On the other hand, in the HIP method, the composite material is encapsulated in a capsule made of a thin plate that is easily plastically deformed, deaerated, or encapsulated with a pressure medium in the capsule, and then subjected to HIP treatment to crush and densify the micropores in the coating. This is the way to do it.

(Problems to be Solved by the Invention) However, with the fusing method, micropores are not removed sufficiently, the quality is easily affected by the skill level of the operator, and since it is remelted with a gas burner, it has a low melting point as a thermal spray material. There is a restriction that a self-fusing alloy must be used. Furthermore, when the sprayed coating is thick, there are parts that are not remelted, making it impossible to improve the quality.

Furthermore, the HIP method involves complicated operations such as encapsulating the composite material in a capsule, which causes a decrease in productivity and an increase in costs.

The present invention was made in view of such problems, and an object of the present invention is to provide a method that can easily and easily remove micropores present in a thermally sprayed coating of a composite material and improve the quality of the thermally sprayed coating. .

(Means for Solving the Problems) In order to achieve the above object, the method for densifying a thermally sprayed coating of the present invention is to densify a composite material on which a thermally sprayed coating has been formed in a vacuum and in a liquid solution of a thermally sprayed material. After melting only the surface of the thermally sprayed coating by maintaining it in a temperature range where the phase and solid phase coexist, the temperature is lowered to a temperature below the solidus temperature of the thermally sprayed material, and then the composite material is hot isostatically pressed as it is. This is the structure of the invention.

(Function) The composite material on which the sprayed coating is formed is desirably IX
Since it is maintained in a vacuum of 10-' torr or less and in a temperature range where the liquid phase and solid phase of the sprayed material coexist (preferably in a temperature range where the liquid phase is 10% or less), the sprayed coating remains in its shape-retaining state. , it is possible to eliminate oxygen (air) in the micropores in the coating and to re-melt the coating surface to seal the openings on the surface.

After melting only the surface of the sprayed coating and sealing the openings on the surface, the temperature of the composite material is lowered to below the solidus temperature of the sprayed material, so that the micropores inside the sprayed coating are in a vacuum ) and whose surface is sealed by a coating of sprayed material is obtained. Therefore, during HIP treatment, sealing and degassing of the composite material becomes unnecessary.

Next, by directly subjecting the composite material to HIP treatment, the micropores inside the thermally sprayed coating are crushed and densified, and the thermally sprayed coating is firmly diffusion bonded to the composite material base material. The HIP processing conditions are the same as before.
Usually, the processing temperature T is Ts≧, where Ts is the solidus temperature.
T≧Q, 8XTs.

The pressure is set to be 700 kg/cJ or more. H over Ts
IP treatment is not preferable because micropores will be generated again during solidification.

The above treatment can be easily carried out by simply charging the composite material into a HIP furnace and adjusting the temperature in addition to normal HIP treatment operations, resulting in extremely high workability.

(Example) A Ni-based self-fusing alloy with the following composition (solidus temperature: 1030°C, liquidus temperature: 1070°C) was sprayed onto a metal substrate (material 335C) with a rectangular cross section by a powder gas spraying method. A composite material with a thermally sprayed coating having a thickness of 3 ml was manufactured.

・Ni-based self-fusing alloy composition (wt%) C: 0.6%, St: 4.0%, Fe: 3
．． 5%, Cr: 16%, B: 3.0%, Co:
Substantially the remainder of the composite material is charged into a HIP furnace and
After holding at 1045°C for 30 minutes at 0-'torr, the temperature was lowered to 850°C.

Next, at 975°C, Ar gas was used as a pressure medium for 100°C.
The pressure was increased to 0 kg/C1a, maintained for 2 hours, and then cooled in a furnace.

From the example sample treated above, 2mm thick x 4mm
A thermally sprayed coating 1 having a width of 30 fl II and a length of 11 mm was cut out by wire-cut electric discharge machining, and a four-point bending test was conducted as shown in FIG. Further, as shown in FIG. 2, a part 2 of the sprayed coating was left on the substrate 3, and the rest was removed from the substrate surface (joint surface), and a shear test was conducted on the joint surface. The dimensional unit in Figures 1 and 2 is ka. The above results are shown in Tables 1 and 2 below. The same table also shows the test results of conventional samples in which the thermally sprayed coating of the same composite material was subjected to fusing.

(Next page) Table 1 4-point bending test results Table 2 Shear test results From Tables 1 and 2, the bending strength of the embodiment of the present invention is about 30% and the shear strength is 40% compared to the conventional example. %, and it is known that the variation in data is extremely small.

(Effects of the Invention) As explained above, according to the method for densifying a thermally sprayed coating of the present invention, the thermally sprayed coating formed on the composite material is melted and solidified only on its surface in vacuum. The microbore within the coating is evacuated, the openings on the surface of the thermally sprayed coating are sealed, and this can be subjected to HIP treatment as is. Therefore, unlike in the past, when performing HIP processing, complicated operations such as enclosing and deaerating the composite material are no longer necessary, and the operations can be simplified.

Then, by the HIP treatment, the microbore in the sprayed coating is crushed, making it possible to make the sprayed coating denser and improve its quality.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a four-point bending test procedure, and FIG. 2 is an explanatory diagram of a shear test procedure on a joint surface. Figure 1j12 Figure

Claims (1)

[Claims] (1) The composite material on which the thermal sprayed coating has been formed is held in a temperature range where the liquid phase and solid phase of the thermal sprayed material coexist to melt only the surface of the thermal sprayed coating, and then the solid phase of the thermal sprayed material is melted. 1. A method for densifying a sprayed coating, comprising lowering the temperature to a temperature below the line temperature, and then subjecting the composite material to hot iso-directional pressing as it is.