The main factors that affect the quality of laser cladding include laser power, cladding speed, lens focal length, focus orientation, maintenance gas, and other process parameters. Laser power and cladding speed are the main parameters that affect cladding quality. The cladding thickness depends on the laser power, which is approximately the 0.7th power of the power (kW). Generally, as the power increases, the cladding depth increases; as the speed increases, the penetration depth changes. Shallow, the weld seam and heat-affected zone become narrower, and productivity increases. However, excessive cladding speed and laser power will increase the tendency of pores and holes. The focal length of the laser cladding lens is determined by the spot diameter of the output laser, and there is an optimal matching value between the two. Generally speaking, the deeper the depth of cladding required, the longer the focal length of the lens. Short focal length lenses have higher requirements for focusing, and powder metallurgy materials spatter during cladding, causing serious lens contamination; lenses with too long focal lengths will suffer from diffraction. Make the focus larger so that the energy density at the focus cannot reach a maximum value. In China, lens-focusing optical systems are generally used. This system can only be used in situations where the laser power is small. Higher laser power will cause the focus of the lens to drift, resulting in poorer weld formation and quality.
Reflector-focusing optical systems are mostly used in higher power situations abroad because of good cooling conditions, good thermal stability, uniform and beautiful weld formation, and reliable cladding quality. The laser cladding laser focus can obtain a large cladding depth at a special position under the workpiece, which is about 1/3 of the plate thickness; the horizontal focus position depends on the situation. The function of the protective gas is to protect the focusing lens and prevent oxidation of the weld. Use inert gas for maintenance, and helium is best. In my country, because helium is expensive, argon is generally used. The gas flow should be controlled well. If it is too small, it will not work; if it is too large, it will waste gas and cause the welding pool to roll, causing waves to appear on the surface of the weld. The bulge of the wave. Laser cladding can be roughly divided into two categories according to the supply method of cladding materials, namely preset laser cladding and synchronous laser cladding. The main process flow of preset laser cladding is base material cladding surface pretreatment – preset cladding material – preheating – laser melting – post heat treatment. The main process flow of synchronized laser cladding is: base material cladding surface pretreatment – feeding laser melting – post-heat treatment. Laser cladding uses a high-energy laser beam (104 ~ 106 W/cm 2) to irradiate the surface of a metal substrate, causing the thin layer on the surface of the metal substrate to interact with the cladding material on it. Through rapid melting and solidification, it forms a layer with high hardness The process of coating a coating with special physical and chemical properties such as good wear resistance and corrosion resistance. This is a new type of composite material that can supplement the excellent properties that the matrix does not have, give full play to the advantages of both, and overcome the shortcomings of each other, thereby significantly improving the wear resistance, corrosion resistance, and resistance of the surface of the base layer. Thermal, antioxidant, and other physical and chemical properties.
Since the 1980s, laser cladding technology has developed rapidly and has become a hot spot in laser surface modification research at home and abroad. Laser cladding technology has great technical economic benefits and is widely used in fields such as machinery manufacturing and repair, automobile manufacturing, textile machinery, navigation and aerospace, and the petrochemical industry.
Laser cladding technology has achieved certain results and is in the initial stage of gradually moving towards industrial application. Future development prospects mainly include the following aspects:
(1) Basic theoretical research on laser cladding.
(2) Design and development of cladding materials.
(3) Improvement and development of laser cladding equipment.
(4) Establishment of theoretical model.
(5) Rapid prototyping skills of laser cladding.
(6) Automation of cladding process control.
