JPS63248465A - Vessel for low-pressure plasma thermal spraying - Google Patents

Abstract

PURPOSE:To favorably hold the low-pressure plasma thermal spraying conditions by providing both a measuring means for measuring the degree of vacuum in a vessel and a holding means for maintaining the degree of vacuum in the vessel at the prescribed value in accordance with the output signal sent from the measuring means. CONSTITUTION:A rotary pump is fitted to a vacuum vessel via a sluice valve. A Bourdon tube-type vacuum gage is fitted as a measuring means and an electrical signal is output. This signal is treated in an arithmetic unit and the motor of the rotary pump is controlled. A vacuum holding means is formed by the arithmetic unit and the rotary pump. The capacity of a vacuum exhaust system is regulated in accordance with the degree of vacuum in the vessel and thereby the balance between it and the amount of gas fed from a plasma thermal spraying gun is held. By such a way, the low-pressure plasma thermal spraying conditions can be favorably held.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a container for low-pressure plasma spraying, and particularly to a low-pressure plasma spraying container that is improved to maintain a constant low-level vacuum. Concerning containers for use.

This is a technology that has been developed and rapidly expanded with improvements in coating materials. However, conventional thermal spraying in the atmosphere causes bubbles, oxides, etc. to be trapped in the coating.
There was a problem in that the properties of the coating material could not be utilized 100%. To solve this problem, a technique has recently been developed to obtain a dense coating without entrainment of oxides by performing plasma spraying in a low-pressure inert gas atmosphere.

Specifically, this method involves plasma spraying in a vacuum container using an inert gas as an arc gas or a powder carrier gas, and the actual degree of vacuum is 50 to 50.
It is about 0 Torr.

(Problems to be Solved by the Invention) As mentioned above, low-pressure plasma spraying involves performing plasma spraying in a vacuum container, but the major problems here are the vacuum or low pressure conditions and the plasma jet. This requires contradictory gas flow conditions. If the capacity of the vacuum evacuation system is too small, the pressure inside the container will quickly rise to over 1 atm due to the plasma jet.
Also.

If the capacity of the exhaust system is large, the vacuum level will exceed the desired level and plasma spraying will not be performed.

We deal with these problems by adjusting the amount of arc gas and opening and closing midsummer valves.
However, with these methods, it is difficult to set satisfactory thermal spraying conditions, and there are problems such as impairing the original function of the valve.

SUMMARY OF THE INVENTION An object of the present invention is to provide a container for low-pressure plasma spraying that solves these conventional problems and satisfies the low-pressure plasma spraying conditions while not placing a burden on the apparatus.

That is, the low-pressure plasma spraying container of the present invention is equipped with a measuring means such as a vacuum gauge attached to a part of the container in order to measure the degree of vacuum inside the container, and furthermore, according to a signal from this measuring means, the vacuum level is measured. The device is characterized by comprising a holding means for controlling the pressure inside the container to a predetermined value by adjusting the evacuation capacity of a vacuum evacuation system such as a pump.

In the low-pressure plasma spraying container of the present invention, the capacity of the evacuation system is adjusted according to the degree of vacuum within the container, thereby maintaining a balance with the amount of gas supplied from the plasma spraying gun.

(Example) A rotary pump having an exhaust capacity of 3000 Q/min was attached to a vacuum container with an internal volume of 2 m3 via a gate valve. A Bourdon tube type vacuum gauge is attached to the container as a measuring means, and the vacuum gauge outputs an electrical signal corresponding to the degree of vacuum. This signal is applied to an arithmetic unit so that the deviation from a predetermined value is calculated. The calculated deviation value is output as an electrical signal and is used as a signal to control the rotary pump motor. In this embodiment, the arithmetic unit and rotary pump form the vacuum holding means.

First, with the motor control circuit turned off, the rotary pump is outputted at 100 meters, and the inside of the container is heated to I
The degree of vacuum was set to about r. When the control circuit is turned on in this state, the signal from the vacuum gauge becomes a much more negative value than the predetermined value (negative values are on the higher vacuum side than the set value), so the output command to the motor becomes almost zero. Next, the gas valve of the vacuum container was opened, argon gas was introduced into the container, and the pressure was increased to a predetermined pressure. At this point, plasma spraying was started.

The signal from the vacuum gauge became a positive value in accordance with the amount of gas supplied from the plasma spray gun, and the output command to the rotary pump increased to maintain a constant degree of vacuum inside the container. At time 2, the amount of gas supplied from the plasma spray gun (1
Since the exhaust capacity of the rotary pump was made sufficiently larger than that of 00Q/min), pressure control with a small range of fluctuation was possible.

〔Effect of the invention〕

By using the container of the present invention, it became possible to maintain low-pressure plasma spraying conditions well.

Agent: Patent Attorney Noriyuki Chika -W

Claims (1)

[Scope of Claims] The invention is characterized by comprising a measuring means for measuring the degree of vacuum in the container, and a holding means for maintaining the degree of vacuum in the container at a predetermined value according to an output signal from the measuring means. Container for low pressure plasma spraying.