KR20180003547U - Vacuum pump components - Google Patents

Abstract

The present invention relates to an improved coating for an inner shaft, rotor and / or stator component of a dry vacuum pump having an improved vacuum pump, particularly a first layer comprising nickel (NiP) in a high phosphorus content, The first layer is coated with a second layer comprising nickel phosphorus and a phosphorous content of high phosphorus content with a fluoropolymer (NiP-PTFE).

Description

Vacuum pump components

The present invention relates to improved coatings for dry pump components such as improved vacuum pumps, especially internal shafts, rotors and / or stator components of dry vacuum pumps.

Dry vacuum pumps are widely used in industrial processes to provide a clean and / or low pressure environment for manufacturing products. Applications include pharmaceutical, semiconductor and flat panel manufacturing industries. Such a pump essentially includes a dry (or oil-free) pumping mechanism, but generally also includes some components, such as a bearing and a transmission gear, for driving a pumping mechanism that requires lubrication to be efficient do. Examples of dry pumps include Roots, Northey [or "claw"], screw and scroll pumps. A dry pump, including roots and / or furnace rotor components, generally includes a stator component that defines a plurality of pumping chambers that each receive a respective pair of intermeshing rotor components. (positive displacement pump). The rotor component is located on a contra-rotating shaft, and may have the same type of profile in each chamber, or the profile may vary from chamber to chamber.

Spheroidal graphite (SG) iron castings have long been used in the manufacture of shafts, stator and rotor components for dry vacuum pumps due to their strength and machinability. However, the high rates of use at elevated temperatures in the semiconductor industry, typically above 150 degrees Celsius, and relatively corrosive gases such as chlorine, boron trichloride, hydrogen bromide, fluorine and chlorine trifluoride, The lifetime of relatively spherical graphite iron shaft, stator and rotor components is relatively short. In fact, as the temperature increases by 10 degrees Celsius, the rate of corrosion almost doubles. Such corrosion can result in equipment failure, process gas leakage, and process contamination as well as costs associated with replacing the pump or corroded parts and resulting process downtime.

In this regard, it is known to passively protect such components by the formation of a resin or polymer coating of a fluoropolymer or polyimide material on the surface of the component exposed to corrosive gases and high temperatures. Such coatings tend to degrade over time and the resulting peeling or flaking of the coating exposes the underlying cast iron to corrosive gases.

Another alternative is to form these components with nickel-rich cast iron, for example, soft Ni-resist or stainless steel with good corrosion resistance. However, Ni-resist cast iron and stainless steels are relatively expensive and difficult to machine, so they do not provide a cost-effective option for the manufacture of rotor and stator components. In addition, the Ni-resist cast iron and stainless steel have a high thermal expansion when used at high temperatures, and thus the performance is degraded.

Another alternative is to form these components with high phosphorous nickel (NiP) content, typically containing 10% to 12% phosphorus. The advantage of high phosphorus NiP plating is that it provides more corrosion resistance because the surface is more uniform and there is no pinhole causing corrosion. In addition, the machinability of the substrate does not change and the addition of NiP plating does not significantly change the thermal properties of the part. However, the use of NiP plating on cast iron and stainless steel in a dry vacuum pump has a major disadvantage that, when there is rotor-to-stator contact, causes anomalous seizure of the pumping mechanism. When sliding contact is made, for example, when the rotating rotor contacts the stator of the dry vacuum pump, surface material can be applied to both components, otherwise known as galling. NiP plating is galvanized when it comes into contact with cast iron, stainless steel or NiP plating itself.

A known approach to preventing galling is to create a NiP-PTFE by incorporating a layer comprising nickel phosphorus and a fluoropolymer (PTFE) into the NiP plating.

Although the use of NiP-PTFE plating solves the problem of galling alone in NiP plating, NiP-PTFE has lower chemical resistance than pure NiP plating of the same thickness.

The purpose of this invention is to overcome this problem by creating a plating with high chemical resistance and preventing galling.

The present invention provides a dry pump component coated with a first layer comprising nickel (NiP) having a high phosphorus content of at least 5 占 퐉 thickness, wherein the first layer comprises at least 5 占 퐉 thick nickel phosphorus and a fluoropolymer (NiP-PTFE), and the ratio of the thickness of the first layer of NiP to the thickness of the second layer of NiP-PTFE is higher than that of the first layer of NiP-PTFE, galling resistance.

Surprisingly, it has been found that a first layer comprising a plating of nickel with a phosphorus content of at least 5 microns and a nickel content of at least 5 microns coated with a second layer comprising nickel (NiP) and a phosphorus content of high phosphorus content with fluoropolymer (PTFE) , It has been found that the combination of at least 5 탆 thick NiP-PTFE coating provides long lasting good corrosion resistance, such as NiP alone, but provides a low galling effect, such as a fluorinated polymer alone.

Other preferred and / or optional aspects of the invention are set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention may be better understood, an embodiment given by way of example only will now be described with reference to the accompanying drawings.

Referring to Figures 1 and 2, a multi-stage dry vacuum pump 10 includes a stator component 12 coated with a first layer 102, preferably comprising a high phosphorus content of nickel (NiP) (NiP-PTFE), having a series of walls defining a plurality of pumping chambers (14, 16, 18, 20, 22) ≪ / RTI > The stator 12 is provided with a suction passage 24 for transferring the gas to be pumped to the inlet pumping chamber 14 and a discharge passage 26 for discharging the pumped gas from the discharge pumping chamber 22 . The circumferential passages 28, 30, 32 and 34 formed in the stator 12 connect the pumping chambers 14, 16, 18, 20, 22 in succession.

The stator 12 receives a first shaft 36 and a second shaft 38 spaced from and parallel to the first shaft 36. The stator 12 has a first shaft 36, The end plates 42, 44 of the stator 12 are provided with bearings 40 that support the shafts 36, 38. One of the shafts 36 is connected to a drive motor 46 and the shafts are coupled together by a timing gear 47 so that in use the shafts 36 and 38 are in the form of arrows 48 and 50, , But at the same speed but in the opposite direction. The gear box 52 attached to the side of the pump 10 includes oil 54 for lubricating the timing gear 47. [

Within each pumping chamber, the shafts 36, 38 support respective rotor components 56, 58, which may also be coated with a first layer 102 comprising a high phosphorus nickel (NiP) content And the first layer is coated with a second layer 100 comprising nickel phosphorus and a phosphorous content of high phosphorus content with a fluoropolymer (NiP-PTFE). In this embodiment, the rotor 56, 58 has a Roots-type profile in each pumping chamber, although a mixture of roots and / or norde-shaped profiles may be provided within the pump 10. Alternatively, the rotor may have a screw-type rotor profile. The rotors 56 and 58 are positioned within each pumping chamber relative to the interior surface of the stator 12 so that the rotors 56 and 58 can operate in a meshing manner known per se.

In use, gas is pumped through the suction conduit 24 into the pump 10 and into the suction pumping chamber 14. The gas is compressed by the rotors 56 and 58 located in the suction pumping chamber 14 and is supplied to the next pumping chamber 16 by the passage 28. The gas supplied into the pumping chamber 16 is likewise compressed by the rotors 56 and 58 therein and is supplied to the next pumping chamber 18 by the passages 30. Similar gas compression occurs in the pumping chambers 18, 20 and 22 and the pumped gas is finally discharged from the pump 10 through the exhaust conduit 26.

(NiP) comprising a high phosphorus content of nickel of at least 5 microns in thickness, wherein the shaft, rotor and / or stator and / or end plate component (12, 42, 44, 56, 58) ) And a second layer comprising a nickel content of at least 5 [micro] m thick and a phosphorous content of high phosphorus content having a fluoropolymer (NiP-PTFE), thereby providing a particularly corrosion resistant A dry vacuum pump is formed. Application of both layers of at least 5 占 퐉 thickness provides a much greater synergy of coating strength and adhesion properties than when only one of the layers is applied to a dry vacuum pump component.

As shown in Figures 3 and 4, the first layer 102 may comprise several coatings of high phosphorus content of nickel phosphorus; That is, the first layer may be made by coating the dry pump component multiple times. For example, by forming a plurality of coatings of nickel phosphorous having a high phosphorus content by electroless plating, a much stronger first layer is formed to reduce the defect continuity of the first layer and reduce the overall porosity of the coating . The total phosphorus content in the first layer is on average 10% to 12%. The first layer of NiP may be formed by a single or multiple coating to form a layer of at least 5 탆 thick, preferably a total first layer thickness of between 6.2 탆 and 15.5 탆.

The second layer 100, which is a matrix of high phosphorus content (NiP-PTFE) containing sub-particles of PTFE (polytetrafluoroethylene), is again formed on the first layer by electroless plating. The total thickness of the second layer is at least 5 [mu] m, preferably from about 8.8 [mu] m to 14.1 [mu] m, but may be larger or smaller, if necessary. Other fluorinated polymers in matrices such as PFA (perfluoroether) or PEI (polyethyleneimine) may also be used.

Example :

In a series of chemical tests on the plated surface, the number of blisters on the 12.5 占 퐉 NiP first layer with a second layer of 12.5 占 퐉 NiP-PTFE (as shown in Figure 3) Lt; RTI ID = 0.0 > NiP < / RTI >

The array test was performed in Atotech plating chemistry. Twenty four cut coupons were exposed to fluorine in the chamber at 200 < 0 > C. Twelve of the cut specimens were provided with a 25 μm base layer of NiP and the other twelve cut specimens had a 12.5 μm base layer of NiP + 12.5 μm top layer of NiP-PTFE.

The cut specimens were weighed before and after the test. The average weight change for each layer system is shown in Table 1 below. There was a slight weight loss for the single plated layer and there was less weight gain for double layer (duplex) plating. The cut specimens were also observed with a Zeiss microscope after 800 hours exposure to fluorine. Taguchi analysis was used to calculate the average number of bubbles found on the surface of each cut specimen. These are shown in Table 1. The average for a single layer is more than twice the number for a bilayer.

Table 1: Average Weight Change and Bubble Number vs. Plating System

This example demonstrates the surprising effect that the use of certain combinations of NiP and NiP-PTFE plating provides excellent chemical resistance to pure NiP plating alone while maintaining the rubbing behavior of NiP-PTFE.

Similarly, any combination of NiP and NiP-PTFE may be used to provide the same advantages as shown above in Table 1 provided that at least a 5 [mu] m base layer of NiP and an at least 8 [mu] m top layer of NiP- PTFE are provided. An example of the ratio of the NiP base layer to the NiP-PTFE top layer is shown in Table 2 below.

Table 2: Specific combination ratio of NiP base layer thickness to NiP-PTFE layer thickness.

Claims (8)

(NiP) with a nickel content of at least 5 microns and a high phosphorus content of at least 5 microns coated with a second layer comprising nickel having a thickness of at least 5 microns and nickel having a high phosphorus content having a fluoropolymer (NiP-PTFE) Wherein the first layer is coated with the first layer,
The ratio of the thickness of the first layer of NiP to the thickness of the second layer of NiP-PTFE provides a high corrosion resistance and anti-
Dry Pump Components. The method according to claim 1,
Wherein the first layer of NiP has a thickness range from about 6.2 [mu] m to about 15.5 [
Dry Pump Components. The method according to claim 1,
Wherein the second layer of NiP-PTFE has a thickness range from about 8.8 [mu] m to about 14.1 [
Dry Pump Components. The method according to claim 1,
The ratio of the first layer of NiP to the second layer of NiP-PTFE is 5 + 20, 5 + 30, 10 + 15, 10 + 25, 12.5 + 12.5, 15 + 10, 15 + 20 + 15, 25 + 5, 25 + 10 or 30 + 5,
Dry Pump Components. 5. The method according to any one of claims 1 to 4,
Wherein the fluoropolymer of the second layer comprises at least one of polytetrafluoroethylene, perfluoroether, and polyethyleneimine
Dry Pump Components. 6. The method according to any one of claims 1 to 5,
The pump component includes at least one of a stator component, an end plate, a rotor shaft component, and a rotor component
Dry Pump Components. The method according to claim 6,
The rotor component may have one of a Norde (claw) rotor, a roots rotor or a screw rotor profile
Dry Pump Components. 8. A method for manufacturing a dry pump comprising the at least one dry pump component according to any one of claims 1 to 7
Dry Vacuum Pump.

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