With the continuous development of social economy, energy conservation, and emission reduction, greenhouse gas emission control and air pollution prevention and control have become current issues that need attention. As a pollution-free and pollution-free new energy for power generation, hydropower has made great contributions to the power industry.
The main failure mode of hydropower flow components is cavitation. Cavitation can cause fish scale pits or sponge-like surfaces on the surface of turbine flow components, destroying the original flow conditions on the surface. In serious cases, it will affect the safe operation of the turbine, especially the runner and blades.
For cavitation corrosion, the common traditional repair and strengthening methods are mainly manual surfacing, flame spraying tungsten carbide coating, and manual application of epoxy coating. This type of method has problems such as high labor intensity, serious on-site dust, noise, and other pollution. The coating and the substrate are physically bonded, and the bonding strength is limited. It will fall off when exceeding the strength limit and within a limited period. The heat-affected zone is large, and the amount of deformation is large.
Huirui pioneered the development of a process technology that uses cobalt-based corrosion-resistant and wear-resistant alloy powder materials to perform laser cladding on the surface of martensitic stainless steel to prepare a surface coating with no structural defects and a gold-gold bond. It has been successfully used in large-scale Hydropower unit repairs strengthens the flow-passing parts of the turbine and achieves good results.
Cavitation resistance performance test
The ZG06Cr13Ni5Mo material and the cobalt-based corrosion-resistant and wear-resistant alloy material laser clad on the surface of ZG06Cr13Ni5Mo were processed to a unified standard sample, in which the cladding sample retained a cladding layer thickness of 0.5mm and was tested according to the same test conditions. Use an ultrasonic accelerated cavitation testing machine to conduct a cavitation resistance comparison test, observe the appearance, weigh and detect, and calculate the amount of cavitation. The test equipment model is YPS17B-HB, the ultrasonic frequency is 20KHZ, the amplitude is 90±10μm, the water temperature is room temperature, and the test time is 0-20h.
From the comparison of the appearance morphology of the samples, it can be seen that after the 20-h accelerated cavitation test, the base material sample showed honeycomb-shaped cavitation holes on the surface, while no cavitation was observed in the laser cladding sample. After 20 hours of accelerated cavitation test, no obvious mass loss was detected in the laser cladding sample.
Metallographic and hardness testing
The test equipment adopts a mobile on-site repair system independently developed by Chengdu Qingshi Laser. The system mainly includes a 4KW semiconductor fiber coupling laser, laser cooling water machine, high-precision 6-axis industrial robot, automatic powder feeder, and software control system.
Application of laser metal additive manufacturing technology in the thermoelectric field
During the operation of the turbine generator unit, due to unclean oil or oil failure and tile burning, the rotor journal will be worn, ranging from grinding marks on the shaft surface to large-area deep grooves and surface defects, which will not only cause the bearing temperature to rise. High, vibration increases, and sometimes even causes accidents such as rolling cracks and detachment of Wujin tiles: journal wear on the sealing tiles of the generator will also affect the tightness of the sealing oil, causing hydrogen leakage from the generator and posing fire hazards. Severe hydrogen pressure drop affects generator output.
Due to factory processing quality issues or long-term wear and tear caused by brush friction, the collector ring of a generator with an excitation system deteriorates the surface shape of the collector ring, resulting in accelerated carbon brush consumption and sometimes causing flashover or ring fire. , in severe cases, it will cause arcing and burn out the carbon brush holder, and even burn out the collector ring.
Highly conductive material coating for power transmission
Preparing a conductive silver layer on the surface of aluminum can effectively reduce its contact resistance and improve its conductivity. Electroplating silver is the most common way to prepare conductive silver layers, but the bonding strength of electroplated silver is low, the service life is short, and the silver electroplating process will have a greater impact on the environment.
Huirui’s laser cladding silver technology has the following advantages
1. The conductivity of the laser cladding silver layer is better than that of the electroplated silver layer, reducing electrical losses during power transmission;
2. The laser cladding silver layer is metallurgically combined with the aluminum matrix to completely solve the problems of wrinkling and peeling. The thickness is greater than the electroplated silver layer, so the quality is stable and reliable, and the service life is longer;
3. The laser cladding silver layer is green and environmentally friendly and has no pollution to the environment;
4. The workpiece can be processed on-site to avoid complicated disassembly and assembly work and save maintenance costs.
