The core performance of alloy cladding wear-resistant steel pipe depends on the bonding strength between the cladding layer and the base pipe. This indicator directly affects the wear resistance, impact resistance, and service life of the alloy cladding wear-resistant steel pipe under complex working conditions. To ensure a robust metallurgical bond between the two, a comprehensive quality control system must be established, encompassing material matching, process control, surface treatment, structural design, parameter optimization, process monitoring, and post-treatment strengthening.
Material matching is the material basis for bonding strength. The thermal expansion coefficients, chemical compositions, and physical properties of the base pipe and cladding layer materials should be as close as possible to reduce the risk of cracking at the bonding surface caused by thermal stress. For example, when the base pipe is carbon steel, the cladding layer often uses nickel-based, iron-based, or cobalt-based alloys. These materials have high compositional similarity to the steel base material and easily form good compatibility after cladding. Simultaneously, appropriate amounts of solid solution strengthening elements (such as Cr and Mo) and hard phases (such as WC and TiC) need to be added to the cladding material to improve wear resistance and enhance the toughness of the bonding interface by refining the grain size.
Process control is a crucial factor determining the bonding quality. Processes such as laser cladding, plasma spraying, or welding of alloy cladding wear-resistant steel pipes require precise control of energy input to ensure that the cladding material forms a deeply fused metallurgical layer with the base pipe surface. Excessive energy will lead to over-melting of the base pipe, resulting in increased dilution and reduced cladding performance; insufficient energy may cause incomplete fusion or porosity defects. For example, during laser cladding, the matching relationship between laser power, scanning speed, and spot size needs to be optimized to ensure the molten pool is in a suitable overheated state, promoting element diffusion and interfacial reaction.
Surface pretreatment is a prerequisite for improving bonding strength. The surface of the alloy cladding wear-resistant steel pipe base pipe needs to undergo rigorous cleaning and activation treatment to remove oil, scale, and rust layers, increasing surface roughness to expand the contact area. Common treatment methods include sandblasting, grinding, or chemical pickling, with sandblasting yielding the best results. It creates uniform pits on the base pipe surface, enhancing mechanical bonding. Additionally, some processes apply an adhesive or transition layer after pretreatment to further eliminate surface defects and provide a high-quality substrate for cladding deposition.
Structural design can help enhance bonding stability. By designing a gradient transition layer or intermediate interlayer between the alloy cladding wear-resistant steel pipe base pipe and the cladding layer, stress concentration caused by differences in material properties can be mitigated. For example, when using composite coating technology, a thin metal layer (such as copper or nickel) is first deposited on the base pipe surface, followed by a wear-resistant alloy layer. The plastic deformation of the intermediate layer absorbs thermal stress, preventing delamination at the bonding surface. Furthermore, the thickness distribution of the cladding layer must be uniform to avoid uneven cooling shrinkage due to localized excessive thickness.
Parameter optimization requires a combination of experimentation and simulation. Through orthogonal experiments or numerical simulations, the sensitivity of process parameters to bonding strength can be determined, finding the optimal combination. For example, in plasma spraying, spraying distance, powder particle size, and gas flow rate all affect coating density and bonding strength, requiring multi-factor interactive analysis to screen key parameters. Simultaneously, ambient temperature and humidity must also be controlled to prevent excessive humidity from causing coating oxidation or increased porosity.
Process monitoring is a crucial means of quality assurance. Online detection technologies (such as infrared thermography and acoustic emission monitoring) can track the bonding state between the cladding layer and the base pipe in real time, promptly detecting defects such as incomplete fusion and cracks. For instance, during laser cladding, monitoring the temperature field distribution of the molten pool can determine if the dilution rate is within a reasonable range, allowing for dynamic adjustment of process parameters. Furthermore, finished product inspection requires a combination of macroscopic inspection and microscopic analysis, such as observing the bonding interface structure using a metallographic microscope or testing bonding strength through tensile tests.
Post-treatment strengthening can further improve bonding performance. Heat treatment (such as annealing or quenching) on the cladding wear-resistant steel pipe can eliminate residual stress and optimize the microstructure. For example, aging treatment of nickel-based coatings can promote the precipitation of hard phases, improving wear resistance while enhancing interfacial adhesion. In addition, machining (such as grinding or polishing) can remove surface defects, improve the smoothness and finish of the bonding layer, and reduce the risk of stress concentration.
