JP2019112723A - Method for treating component to prevent erosion of the component - Google Patents

Abstract

To provide a method for treating a surface of a component to improve wear resistance to liquid droplet erosion and to erosion deriving from cavitation phenomena.SOLUTION: Provided is a high velocity spray method for treating a surface of a component (C), comprising the steps of: heating a first portion of an inert gas up to a spray temperature (T3) between 550°C and 800°C; preparing a powder material having a composition including Co at a mass percentage between 15% and 70%; preparing a mixture between the powder material and a second portion of the inert gas; mixing the first portion of the inert gas and the mixture of the gas and the powder in a spray gun (60) to create a spray jet; and directing the spray jet toward the surface to be treated to deposit a coating (S) of the material comprising Co.SELECTED DRAWING: Figure 2

Description

    The present invention relates to a method for treating the surface of a component that is subject to erosion by a liquid or by a cavitation phenomenon. The invention also relates to a component comprising a surface treated in such a way, and an apparatus for carrying out such a method.

    It is well known to apply a wear resistant alloy coating to the surface of a substrate material to improve its resistance to erosion. For components of rotary machines such as steam turbines, centrifugal and axial compressors, pumps, and other rotary machines, in particular, they exhibit a sufficient degree of resistance to erosion from droplet erosion or cavitation phenomena is important. For example, in a steam turbine, droplet erosion typically occurs along the leading edge of the blade (FIG. 1).

  Known methods for applying erosion resistant coatings to such surfaces include surface hardening, laser cladding, brazing and welding.

  The above techniques usually involve heat input to the substrate material, which typically determines the following disadvantages. That is, the presence of a heat-affected zone where the component may not conform to the NACE standard, distortion of the coated component, the need for post heat treatment, cracking, iron dilution in the coating, and uneven microstructure is there.

    Furthermore, the above techniques can not be used to deposit coatings that include non-weldable materials.

    Therefore, it is desirable to provide an improved method for treating the surface of a component that can avoid the above-mentioned drawbacks.

European Patent Application Publication No. 2175050

According to a first embodiment, the present invention achieves such an object by providing a method of treating the surface of a component, the method comprising
Heating a first portion of the inert gas to a spray temperature (T3) of 550 ° C to 800 ° C;
Preparing a powder material having a composition comprising Co at a weight percentage of 15% to 70%;
Preparing a mixture of the powder material and the second portion of the inert gas;
Mixing the first portion of the inert gas and the mixture in a cold gun to produce a spray jet;
Directing a spray jet towards the surface to deposit a coating of material;
including.

 The solution according to the invention makes it possible to deposit a coating on the surface of the substrate material in order to improve the resistance to erosion. The following mechanical properties can be achieved with the coatings thus produced: That is, hardness (Vickers): 400 <HV <1000, and porosity: <2%.

In a second embodiment, the above advantages are achieved by an apparatus comprising: A first heater for preheating the first portion of the inert gas to a preheating temperature (T1) of 400 ° C. to 500 ° C .;
Powder having a final heater for heating the first portion of the inert gas to a spray temperature (T3) of 550 ° C. to 800 ° C., and a composition comprising the inert gas and Co at a weight percentage of 15% to 70% A supersonic nozzle for producing a spray jet comprising the material;
A powder feeder for preparing a mixture of powder material and a second portion of inert gas;
At least a first duct for connecting the first heater to the final heater;
At least a second duct for connecting the powder feeder to the supersonic nozzle;
A device that includes

    Other objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention in conjunction with the following drawings.

2A and 2B are two different views of a prior art component that has been subjected to droplet erosion. FIG. 1 is a schematic view of an apparatus for performing the method according to the invention. Figure 3 is a schematic view of the components of the device of Figure 2;

  The present invention provides a method for treating the surface of a component, in particular for the improvement of the wear resistance to erosion from droplet erosion and cavitation phenomena. In particular, but not exclusively, the invention applies to components of rotary machines such as steam turbines, centrifugal and axial flow compressors, and pumps.

  The method utilizes high speed spray technology to apply a coating of ductile material to the surface of the component.

  Referring to FIG. 2, an apparatus for implementing the method according to the invention is indicated generally by the numeral 1. The apparatus 1 comprises an upstream duct 10 connecting a pressurized carrier gas source 15 to a first gas heater 20 and a powder feeder 30, both of which are conventionally used. Are known types and are therefore not described in detail. The carrier gas is nitrogen or helium or other convenient inert gas. The carrier gas flows through the apparatus at a pressure of 20 bar to 50 bar. The flow rate of the carrier gas is 2 m 3 / hour to 6 m 3 / hour.

  The upstream duct 10 has a first main branch 11 connecting the gas source 15 to the first gas heater 20 and a secondary branch separating from the first main branch 11 to connect the gas source 15 to the powder feeder 30. And 12. On the downstream side of the intersection of the two branches 11 and 12 of the upstream duct 10, the main branch 11 and the secondary branch 12 are used to adjust or stop the flow of carrier gas in the main branch 11 and the secondary branch 12. And second valves 13, 14 respectively.

  In the first gas heater 20, the first portion of the carrier gas is preheated to a preheating temperature T1 of 400 ° C to 500 ° C. On the downstream side of the first gas heater 20, the preheated carrier gas flows in the first downstream duct 40 connecting the first gas heater 20 to the spray gun 60. Along the first downstream duct 40, the temperature of the carrier gas drops to the discharge temperature T2 immediately upstream of the spray gun 60. The release temperature T2 is lower than the preheat temperature T1, and is 350 ° C to 450 ° C.

  In the powder feeder 30, the second portion of the carrier gas flowing from the secondary branch 12 of the upstream duct 10 is mixed with a spray powder of ductile material having a composition containing Co at a weight percentage of 15% to 70%. Be done. For example, ductile materials that can be used for the spray powder according to the invention include Stellite® 6, Stellite® 12, Stellite® 21 and US It contains the material defined in Patent No. 6986951.

  On the downstream side of the powder feeder 30, the mixture of carrier gas and spray powder flows in a second downstream duct 50 connecting the powder feeder 30 to the spray gun 60.

  The spray gun 60 extends along the longitudinal axis X and comprises a final heater 61 and a supersonic nozzle 62, which is connected downstream of the latter to the final heater 61. In operation, the spray gun 60 is housed within the spray enclosure 70 with the surface of the component C to be sprayed with the coating S of spray material. The surface to be sprayed is disposed within the housing 70 perpendicular to the longitudinal axis X.

  Referring to FIG. 3, the final heater 61 comprises an outer housing 67 and a heating chamber 66, which is directly upstream of the supersonic nozzle 62 from an inlet 63 connected to the first downstream duct 40. Extending along the longitudinal axis X to the outlet portion 64. The carrier gas from the first downstream duct 40 flows from the inlet 63 through the heating chamber 66 to the outlet 64. In the heating chamber 66, the carrier gas is again heated to the spray temperature T3 of 550 ° C. to 800 ° C., which is higher than the discharge temperature T2. The final downstream portion of the second downstream duct 50 is coaxial with the longitudinal axis X and passes through the heating chamber 66 to a final portion 65 just upstream of the supersonic nozzle 62. The outlet portion 64 of the heating chamber 66 annularly surrounds the final portion 65 of the second downstream duct 50. On leaving the final heater 61, i.e. on leaving the last downstream part of the heating chamber 66 and the second downstream duct 50 respectively, a first part of the reheated carrier gas, and a second of the powder and carrier gas. The mixture with the part of the mixture mixes with each other to form the spray jet 80 and enters the supersonic nozzle 62.

  At the supersonic nozzle 62, the spray jet 80 expands and the powder particles reach a velocity v. The spray jet 80 is directed towards the surface of the component C by means of a supersonic nozzle 62 in order to apply the coating S. The value of velocity v is typically greater than 300 m / s when the carrier gas is nitrogen and greater than 1000 m / s when the carrier gas is helium, and the deposition efficiency is typically 80% Greater than.

    With the deposited coating S, the following mechanical properties can be achieved. That is, hardness (Vickers): 400 <HV <1000, and porosity: <2%.

DESCRIPTION OF SYMBOLS 1 apparatus 10 upstream side duct 11 1st main branch 12 secondary branch 13 1st valve 14 2nd valve 15 gas source 20 1st gas heater 30 powder feeder
40 first downstream side duct 50 second downstream side duct 60 spray gun 61 final heater 62 supersonic nozzle 63 inlet 64 outlet 65 final 65 heat chamber 67 outer housing 70 spray housing 80 spray jet C component S Coating T1 Preheating temperature T2 Discharge temperature T3 Spray temperature

Claims (7)

A high speed spray method for treating the surface of component (C),
Heating a first portion of the inert gas to a spray temperature (T ₃ ) of 550 ° C. to 800 ° C .;
Providing a powder material having a composition comprising at least one of Stellite® 6, Stellite® 12 and Stellite® 21;
Providing a mixture of the powder material and a second portion of inert gas;
Mixing the first portion of the inert gas and the mixture in a spray gun (60) to produce a spray jet (80);
Directing the spray jet (80) towards the surface to deposit a coating (S) of the material;
Method including. The heating step is preceded by a preheating step in which the first portion of the carrier gas is preheated to a preheating temperature (T ₁ ) lower than the spray temperature (T ₃ ) and 400 ° C. to 500 ° C. The method according to claim 1.   The method according to claim 1, wherein the inert gas is nitrogen and / or helium.   The method according to claim 1, wherein the pressure of the carrier gas upstream of the spray jet (80) is between 20 bar and 50 bar. An apparatus for spraying on the surface of component (C),
A first heater (20) for preheating the first portion of the inert gas to a preheating temperature (T ₁ ) of 400 ° C. to 500 ° C .;
A final heater (61) for heating the first portion of the inert gas to a spray temperature (T ₃ ) of 550 ° C. to 800 ° C., the inert gas, and Stellite® 6, Stellite ( A supersonic nozzle (62) for producing a spray jet (80) comprising a powder material having a composition comprising at least one of: registered trademark 12 and Stellite 21 21; )When,
A powder feeder (30) for preparing a mixture of the powder material and a second portion of inert gas;
At least a first duct (40) for connecting the first heater (20) to the final heater (61);
At least a second duct (50) for connecting the powder feeder (30) to the supersonic nozzle (62);
Devices that contain   A component (C) comprising a surface treated by the method according to any one of the preceding claims. The component (C) according to claim 6, wherein the component (C) is a steam turbine blade.