JPS5943990B2 - Surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating the surface of a refractory thermal spray coating or a refractory object.

For example, in some engines, a refractory spray coating is formed on the surfaces of heat-insulating, heat-resistant, high-temperature members such as pistons, valves, exhaust passages, etc., or the engine itself is made of a refractory material in order to increase its efficiency.

However, since the thermal spray coating is merely mechanically bonded to the metal surface, and as mentioned above, there are many pores on the surface and inside the coating, it is easy for particles to fall off, peel off, and even crack. . In addition, refractories made of refractories themselves similarly have pores on the surface and inside, which can cause cracks, resulting in inadequate durability and lack of stability. This tendency is remarkable when the number of pores is increased to improve properties. The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a thermally sprayed refractory coating or a refractory object with excellent durability and surface stability without impairing its thermal insulation properties. The present invention provides a processing method. That is, the present invention uses a slurry in which a binder mainly composed of ethyl silicate is mixed with refractory powder made of fine silica flour or zircon flour of 300 mesh or less,
A method for surface treatment of refractories, which comprises applying a porous sprayed refractory coating to the surface of a refractory component or a porous refractory component placed between a combustion chamber and an exhaust passage exposed to combustion gases of an engine, and then firing the coating. It is.

The method of the present invention will be explained in detail below.

The method of the present invention is applied to the surface of a refractory sprayed coating or a refractory object.
A mixture of fine refractory powder of 0 mesh or less and engineered silicate is applied and fired.

A porous refractory thermal spray coating or a refractory component has many pores that are open on the surface, but according to the method of the present invention, by applying the above-mentioned fine refractory powder mixture, this mixture can be removed. penetrates the surface pores and seals them.

Then, by drying and firing this, a hard surface coating layer containing the above-mentioned refractory powder as a main component is formed on the surface. As a result, the thermal spray coating or the surface particles of the refractory component can be continuously covered with the surface coating layer to prevent the particles from falling off. Furthermore, when an external force is applied, this surface coating layer protects the refractory component or the thermal spray coating and prevents it from peeling or cracking. As the refractory parts used in the method of the present invention, A
l2O3SiO2, ZrO2, Al2O3, SlO2,
It is made of a refractory material such as ZrO2-SiO2, and is used, for example, in parts that require heat insulation and heat resistance, such as engine pistons, valves, and exhaust passages.

In addition, the porous sprayed coating is made of ZrO2, A'203, or Ni-Al, Ni-Cr-MO, Ni-Cr.
- It is a mixture of a binder such as Al, and is coated on the surfaces of, for example, metal pistons, valves, exhaust passages, etc. The slurry applied to refractory objects is a mixture of a binder and a refractory powder consisting of fine silica flour or zircon flour of 300 mesh or less.

The reason why the particle size of the refractory powder is limited to 300 mesh or less is that if the powder is coarser than this, it will not be possible to obtain a uniform slurry, and defects will easily occur in the surface coating layer obtained by firing. be. The mixing ratio of the refractory powder is preferably 150 to 350 parts by weight when using silica flour, and 250 to 450 parts by weight when using zircon flour, based on 100 parts by weight of the binder. In addition, the above binder is mainly composed of ethyl silicate, and alcohol, water, hydrochloric acid, etc. are added thereto. For example, ethyl silicate 4
When 0 is used, it is preferable that the amount of ethyl silicate 40 contained in the binder is 30 to 60 parts by weight.

Furthermore, the firing temperature range of the applied slurry varies depending on the type of material to be coated, but is 800 to 1,500°C or less, the firing time varies depending on the temperature, but is practically preferably 0.5 to 5 hours, and the firing atmosphere is not particularly limited. do not have.

Next, an embodiment in which the present invention is applied to an exhaust passage core of an automobile engine will be described.

First, Al2O3-SiO2-based refractory powder is used as a raw material,
After forming this into a cylindrical shape using the slip casting method, 1
An exhaust passage core 1 as shown in FIG. 1 was produced by sintering at 450°C.

In this case, the core 1 has about 30% porosity. Next, 50 parts by weight of ethyl silicate 40, alcohol 43
A binder was prepared by mixing 1 part by weight, 6 parts by weight of water, and 1 part by weight of hydrochloric acid, and 350 parts by weight of fine silica flour of 3-00 mesh or less was mixed with 100 parts by weight of this binder to prepare a slurry. This slurry was poured into the inner surface of the exhaust passage core 1 and applied thereto. When the applied slurry was removed in this state, it was confirmed that the slurry had penetrated into the surface pores of the core 1 and the pores had been sealed. Next, the exhaust passage core 1 coated with the slurry in this way was heated to a temperature of 25°C ± 5°C.
After repeating the process of drying in a drying oven maintained at a relative humidity of 50 to 60 (f) to volatilize the solvent 5 times,
It was fired at 450°C.

As a result, as shown in enlarged view in FIG. 2, a surface coating layer 2 mainly composed of extremely hard SlO2 was formed on the inner surface of the exhaust passage core 1. In addition, 3 in the figure is the exhaust passage core 1
These are the pores formed inside the . Note that this exhaust passage core 1 is cast into the engine head when it is cast. As is clear from the above results, according to the method of the present invention, a mixture of a binder and refractory powder is applied and then fired to form a hard surface coating layer on the surface of the refractory. It prevents particles from falling off, peeling off, and even cracking, increasing durability and surface stability, and also has excellent heat insulation effects. It is extremely suitable for surface treatment.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an exhaust passage core subjected to the method of the present invention;
FIG. 2 is an enlarged sectional view of the main part of the core. 1...Exhaust passage core, 2...Surface coating layer, 3...Vacancy.

Claims (1)

[Claims] 1 30 to a binder whose main component is ethyl silicate
A porous refractory thermal spray coating or refractory parts that is coated with a slurry mixed with refractory powder made of fine silica flour or zircon flour of 0 mesh or less is placed from the combustion chamber exposed to the combustion gas of the engine to the exhaust passage. A surface treatment method comprising applying the coating to the surface of the substrate and then baking it to form a surface coating layer.