Air valve face powder plasma surfacing layer pore repairing method and device

Abstract

The invention discloses an air valve face powder plasma surfacing layer pore repairing method and device, belongs to the field of welding additive manufacturing, is used for solving the problem that surfacing layer pore defects are prone to occurring in the ion surfacing process, and particularly relates to an air valve face powder plasma surfacing layer pore repairing device and method. According to the pore repairing device, resistance heating and a pressurizing mechanism are combined, so that pore repairing in a surfacing layer is promoted under certain temperature and pressure conditions. According to the pore repairing method, a resistance direct heating technology is adopted, a surfacing layer pressurizing device is combined, and the healing of pores in a surfacing layer is promoted by accurately controlling the heating and pressurizing processes.

Description

Technical Field

[0001] The present invention proposes a method and device for repairing pores in a powder plasma surfacing layer on a gas valve surface, belonging to the field of welding additive manufacturing, and specifically includes a repair device that combines direct resistance heating and pressurization to perform pore repair in conjunction with a corresponding process. Background Art

[0002] During the service of marine diesel engines, the valve surface must have sufficient strength to withstand repeated impact loads, and must also have strong high temperature resistance to adapt to the thermal shock service environment caused by high temperature and high pressure gas. In order to improve the wear resistance, corrosion resistance and high temperature resistance of the valve sealing surface, plasma surfacing technology is often used for surface strengthening. During the plasma surfacing process, due to the influence of process parameters, molten pool cooling rate and gas inclusions, pore defects may appear in the valve surfacing layer. Porosity is a small bubble formed by the failure of gas or impurities to be completely discharged or dissolved during welding. It is usually located inside the weld metal or at the weld joint. In a high temperature and high pressure working environment, the presence of pores will cause the valve sealing surface to be prone to local overheating, stress concentration and early fatigue rupture, significantly reducing the service life of the valve and affecting the safe operation of the diesel engine. During the plasma surfacing process, the repair method of pore defects can draw inspiration from the self-repair mechanism in organisms. The self-repair phenomenon of organisms after tissue damage is widely present, and damaged cells repair wounds by division and repair. In the inanimate metal world, although metals do not have complete self-repair capabilities, some studies have shown that under certain conditions, metal alloys can undergo similar self-repair processes. Summary of the invention

[0003] In response to the problem of repairing pore defects in plasma surfacing layers described in the background technology, the present invention provides a repair device that combines direct resistance heating with pressurization, which can effectively promote the healing of pores in the surfacing layer and significantly improve the density and mechanical properties of the surfacing layer. The device specifically includes a pore repair device and a pore repair method for a powder plasma surfacing layer on a valve face.

[0004] The pore repair device combines resistance heating with a pressurization mechanism to heat the weld overlay layer through the heat generated by the electric current while applying uniform pressure, thereby promoting the repair of pores in the weld overlay layer under certain temperature and pressure conditions. The entire pore repair device includes four major systems, namely the resistance heating system, the pressure control system, the temperature monitoring system, and the workbench and fixture system. The resistance heating system consists of electrodes, a heating power supply, and a heating controller; the temperature monitoring system consists of a thermocouple sensor, a temperature data acquisition system, and a temperature controller; the pressure control system consists of a four-petal pressurization device and a pressure sensor; the workbench and fixture system consists of a stable workbench and a gas valve fixing fixture.

[0005] The resistance heating system is composed of electrodes, a heating power supply and a heating controller. The system connects the pressurized electrode to the positive electrode and the workbench electrode to the negative electrode. The current forms a loop through the power supply-pressurized electrode-welding layer-workbench to complete the current flow and heating process. The heating controller monitors the temperature in real time and adjusts the current according to temperature feedback to ensure that the welding layer remains within the optimal repair temperature range.

[0006] The temperature monitoring system and the temperature controller adjust the heating device according to the real-time temperature feedback to ensure that the temperature of the cladding layer is always within the required range.

[0007] The pressure control system and the pressure sensor monitor the pressure applied to the cladding layer in real time and feed the data back to the control system to ensure that the pressure is stable and uniform, so as to avoid defects in the cladding layer caused by uneven or excessive pressure.

[0008] The workbench and fixture system, the workbench provides a stable support platform to ensure that the gas valve remains in a fixed position throughout the repair process; the gas valve fixing fixture is used to accurately position the gas valve and ensure that it is aligned with the heating device, electrode, and pressurizing device to ensure the heating and pressurizing effects during the repair process.

[0009] The pore repair method adopts the resistance direct heating technology and combines it with the weld overlay layer pressurizing device. The weld overlay layer is softened by precisely controlling the heating to improve the plastic deformation capacity. The metal near the pores in the weld overlay layer is deformed by precisely controlling the pressurizing until the pores are healed, so as to improve the density of the weld overlay layer and further enhance its mechanical properties and high temperature resistance.

[0010] The present invention is suitable for powder plasma surfacing of valve surfaces, accurately controls the heating and pressurizing process, promotes the healing of pores in the surfacing layer, improves the density of the surfacing layer, and further improves its mechanical properties and high temperature resistance. The present invention adopts a method combining resistance heating and pressurizing mechanism, heats the surfacing layer through the heat generated by the current, and applies uniform pressure at the same time, thereby promoting the repair of pores in the surfacing layer under certain temperature and pressure conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the resistance heating and pressurization experimental apparatus.

[0012] Figure 2 This is a diagram of the layout of the heating and pressurizing device.

[0013] Figure 3 Schematic diagram of the current during the repair process. DETAILED DESCRIPTION

[0014] The present invention is described in detail below with reference to the accompanying drawings and specific implementation modes.

[0015] refer to Figure 1 , the resistance heating and pressurizing experimental device in this specific embodiment is introduced. First, the gas valve after plasma surfacing is fixed in the fixture system 1 on the workbench. The fixture 1 aligns the gas valve 2 with the heating device 8, the electrode 5 and the pressurizing device 4. The electrode is installed on the surface of the surfacing layer. According to the behavior of the current when passing through the material, the current will preferentially choose a path with lower resistance to flow. Therefore, when the electrode is installed close to the surface of the surfacing layer, it can ensure that the current acts more directly on the pore area and promote pore repair and healing.

[0016] The specific conditions of the workpiece and the implementation process are described below. This implementation case is illustrated by repairing pores in a powder plasma cladding layer on a gas valve surface.

[0017] Fix the gas valve after plasma cladding in the fixture system on the workbench to ensure that the gas valve maintains a stable and precise position during the repair process. The fixture aligns the gas valve with the heating device, electrode and pressure device to ensure uniform force and heating of the cladding layer during the heating and pressure process.

[0018] Start the resistance heating system, the electrode generates heat through the current and transfers the heat to the surface of the gas valve cladding layer. The heating controller adjusts the current intensity in real time according to the feedback signal of the temperature sensor to ensure that the cladding layer is always within the optimal repair temperature range.

[0019] In welding repair, the optimal repair temperature range of the cladding layer is closely related to the melting point of the material, the heat treatment characteristics, and the physical and chemical changes required for the repair. If combined with common cladding materials (such as stainless steel, nickel-based alloys, etc.) and the repair process, the possible repair temperature range is generally between 300°C and 1200°C, depending on the material used. For the precise temperature range, it is necessary to consult the standards in the technical field or obtain it through experimental data.

[0020] The temperature monitoring system measures the temperature of the cladding layer in real time and transmits the data to the temperature data acquisition system to ensure that the temperature control system accurately maintains temperature stability. By accurately adjusting the heating power, the cladding layer is heated evenly to avoid unsatisfactory repair effects due to local overheating or excessive temperature fluctuations.

[0021] After the resistance heating system is started and the cladding layer is heated evenly, the pressurizing device is turned on. Under the action of the driving force, the four-petal pressurizing device approaches the cladding layer on the valve face until it fits tightly with it, and then stops moving. The driving force will continue to act on the pressurizing device to form a uniform pressure, which is usually not high, between 10 2 N-10 4N, the actual value setting needs to comprehensively consider the material and size of the weld overlay and the pressure device. The purpose of setting a lower pressure is to evenly distribute the contact force between the four-petal pressure device and the valve surface weld overlay, while avoiding excessive pressure on the valve surface weld overlay and damage to the pore position.

[0022] The completion of pore repair is determined by monitoring the temperature and pressure changes of the weld overlay layer. When the temperature control system keeps the weld overlay layer within the optimal repair temperature range and the temperature is stable at a predetermined value, combined with the pressure control system that uniformly applies pressure, if the pore defects are significantly reduced or disappear, and the surface is flat and dense, it means that the pores have healed. At this time, the system stops the heating and pressurization process.

[0023] For temperature, if we usually assume that the temperature range is between 300℃ and 1200℃, then the best repair effect may be achieved within this range; for pressure, it is usually between several hundred and several thousand Newtons, which is precisely controlled according to the repair requirements. Therefore, the exact value may need to be confirmed through actual engineering design or experimental research.

Claims

1. A method and device for repairing pores in a powder plasma cladding layer on a valve surface, which solves the problem of pore defects in the cladding layer that are prone to occur during ion cladding, and is specifically a pore repairing device and a pore repairing method for a powder plasma cladding layer on a valve surface, wherein the pore repairing device is characterized by: The resistance heating is combined with a pressurizing mechanism, the weld overlay layer is heated by the heat generated by the electric current, and uniform pressure is applied at the same time, and the pore repair in the weld overlay layer is promoted by temperature and pressure control. It is composed of a resistance heating system, a pressure control system, a temperature monitoring system, a workbench and a clamp system; the pore repair method is specifically manifested in the use of resistance direct heating technology combined with a weld overlay pressurizing device, which promotes the healing of pores in the weld overlay layer by precisely controlling the heating and pressurizing process.

2. A method and device for repairing pores in a gas valve surface powder plasma cladding layer according to claim 1, characterized in that The resistance heating system in the pore repair device is composed of electrodes, a heating power supply and a heating controller. In the resistance heating system, the electrodes transfer heat to the gas valve cladding layer through electric current to ensure that the cladding layer is evenly heated during the repair process; the heating power supply provides adjustable current to accurately control the temperature during the heating process.

3. A method and device for repairing pores in a gas valve surface powder plasma cladding layer according to claim 1, characterized in that The pressure control system in the pore repair device is composed of a four-petal pressurizing device and a pressure sensor. The four-petal pressurizing device completely wraps the gas valve surfacing layer and evenly applies pressure to the surface of the surfacing layer to ensure that the surfacing layer is evenly stressed during the heating repair process.

4. A method and device for repairing pores in a gas valve surface powder plasma cladding layer according to claim 1, characterized in that The temperature monitoring system in the pore repair device is composed of a thermocouple sensor, a temperature data acquisition system and a temperature controller. The thermocouple sensor is installed on the surface of the surfacing layer to measure the temperature in real time and transmit the data to the temperature data acquisition system.

5. A method and device for repairing pores in a gas valve surface powder plasma cladding layer according to claim 1, characterized in that The workbench and fixture system in the pore repair device consists of a stable workbench and a gas valve fixing fixture; the workbench provides stable support to ensure that the gas valve remains in a fixed position during the entire repair process; the gas valve fixing fixture is used to accurately position the gas valve and ensure that it is aligned with the heating device, electrode, and pressurizing device to ensure the heating and pressurizing effects during the repair process.

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