The plunger pump is an important equipment in oil and gas production, widely used in fracturing, cementing and water injection. As a key component of the plunger pump, the plunger rod is vulnerable to friction damage caused by high-frequency reciprocating motion and erosion of medium corrosion and hard particles during the working process, and its service life is only 15 to 35 days.
Large oil fields will have thousands of water injection pumps, every year will produce a large number of waste plunger rods. In order to repair the old benefit waste and help enterprises achieve the purpose of reducing costs and increasing efficiency, Xi 'an Guosheng laser has developed and applied remanufacturing and surface strengthening technology for many years. It based on high-speed laser cladding technology are carried out for waste plunger rods.
The traditional surface treatment processes of plunger rod include electroplating, spray welding and so on. Electroplating has been gradually eliminated due to environmental pollution and poor coating performance. Although spray welding Ni60 technology can obtain suitable surface strengthening layer properties, due to large heat input, it not only has obvious influence on the mechanical properties of the matrix but also has serious deformation. After machining, the thickness uniformity of the effective cladding layer is poor, which makes it easy to deform the joint of the plunger rod and lead to scrap of the workpiece. Therefore, the flame spray welding technology is not suitable for the remanufacturing of the plunger rod, and the plunger rod surface strengthened with this technology is not suitable for the remanufacturing of the blank.
Different from traditional laser cladding, high-speed laser cladding by changing the action process of laser and powder, melt or semi-melt the powder on the molten pool, melt or semi-melt liquid flow into the molten pool, forming a metallurgical bonding surface coating, its cladding efficiency and surface quality can be improved. Compared with spray welding and traditional laser cladding, it has the advantages of high efficiency, low heat input, low dilution rate, thin coating, flat surface and small amount of follow-up processing.
High-speed laser cladding has obvious advantages in product quality and influence on the matrix. It can be used not only for surface strengthening but also for plunger rod remanufacturing.
According to the difference of work nature and damage mode, the plunger rod is divided into A, B and C three areas according to the outer surface.
1. Area A is the connection position of the plunger rod and the crosshead tappet. Due to size reduction and sudden change, it is the mechanically weak area of the whole workpiece, which is prone to fracture and deformation, and there is slight pitting and rust.
2, Area B is the main working face of the plunger rod, but also vulnerable surface, there are obvious scratches and pitting pits on the surface, is the main part of high-speed laser cladding remanufacturing.
3. Area C is the end face of direct contact between the plunger rod and the liquid, and there is obvious corrosion, especially serious corrosion at the center hole (or sediment erosion). For deeper corrosion or erosion holes (more than 2mm), manual argon arc welding is used to restore the size and then high-speed laser cladding treatment.
Remanufacturing or surface strengthening plunger rods with high-speed laser cladding technology has the following features
1. Low heat input, small deformation, high efficiency, uniform thickness of cladding layer, little damage to the matrix life.
2. The high-speed laser cladding is used to strengthen the surface of the plunger rod, which can also be remanufactured after use, saving the raw material procurement cost and part of the machining work of the rod body.
3. The dilution rate of high-speed laser cladding does not exceed 3%, and the thinner cladding layer thickness (0.2mm) can meet the requirements and reduce powder waste.
4. The surface roughness of high-speed laser cladding is as low as Ra12.8m, which can be processed directly by grinding machine.
5. The hardness of the metal matrix composite powder cladding layer is greater than HRC55, the wear resistance and corrosion resistance of the cladding layer are not lower than that of spray welding Ni60, the thickness of the cladding layer is uniform, and the thickness difference of the cladding layer is less than 5 microns after machining, and the service life of the plunger rod is greatly improved.
6. With high-speed laser cladding technology as the core, the whole plunger rod remanufacturing process is green, environmental protection and pollution-free.