1 Composite coating technology
Research results show that the composite surface strengthening treatment is not a simple single superposition process, but to achieve the effect of 1+1>2 in the process of multiple process technology composite treatment, through a combination of 2 or more than 2 kinds of process technology to achieve the strengths and weaknesses of the composite performance and effect.
A S KORHNEN et al. through the plasma nitriding and then physical vapor deposition process combination, the development of a new penetration plating composite treatment (PN/PVD) technology, the complementary two surface strengthening technology to make up for some of the performance shortcomings of a single surface strengthening technology. Through the organic combination of the matrix, nitriding layer, metal layer, transition layer, plating layer, to play the performance characteristics of each layer of the advantages of the nitriding layer to improve the hardness of the matrix at the same time can play a support to reduce the role of the hardness gradient between the membrane layer and the matrix, so that the membrane layer load-bearing capacity has been improved to reduce the risk of failure due to the load caused by the membrane layer falling off too much. This smoother change in the hardness gradient results in a reduction of the coating force when the external load is applied, and a more uniform distribution of stress at the interface. This also makes it more load-bearing than simple PVD coatings, making it suitable for working environments with harsher friction and wear conditions and longer service intervals.
SHI W et al. By comparing the surface of Cr12MoV die steel magnetron sputtering deposition of Ti / TiN coating and low temperature ion carburizing and then PVD deposition of Ti / TiN film composite treatment process, the mold parts surface strength and hardness has been enhanced, and carburization after the coating performance is better. Yang Jiuzhou et al. first used ion nitriding technology combined with multi-arc ion plating to strengthen the 40Cr steel substrate, hard CrN coating deposited on the surface of the substrate, so that the substrate, nitriding layer, CrN coating to form a hardness gradient, not only to enhance the multi-arc ion plating CrN coating wear resistance, while reducing the risk of coating peeling off and failure. Zhang Haizhou et al. through the composite PVD coating die surface treatment process verification, to solve the strain defects in the production of thin plate stamping, shorten the mold assembly time and debugging cycle and reduce manufacturing costs. The composite treatment method of penetrating and plating solves the shortcomings of a single process to a certain extent, and makes the composite treatment layer harder, more wear-resistant, and more load-bearing capacity.
Roll embossing has received more and more attention in recent years due to its fast and continuous mass production process. The microstructure on the surface is a challenge for the manufacturing of rolls, HUANG T G et al. proposed a method to prepare microstructures on the surface of roll dies using a new type of step rotary lithography and chemical nickel plating technology to prepare micro groove roll microstructures with an average height of 1.1 μm and widths of 23, 45 μm on metal rolls. Composite coating technology in the direction of coating refinement and provide film layer functionality still has a broad space for development, the organic combination of a variety of coating technologies has a certain development potential and possibilities.
2 Nano-coating technology
Nanocomposite coatings can be prepared by adding nanoparticles to traditional coating materials and utilizing the properties of zero-dimensional or one-dimensional nanopowder materials through fabrication processes such as vapor deposition, spraying, electroplating, or chemical plating [54].R SCHWETZKE et al. In the process of preparing nano WC/12Co and WC/15Co coatings by thermal spraying, the rapidity of the supersaturated Co (W, C) matrix under the impact of the particle solidification leads to the formation of amorphous or nanocrystalline phase, nanoparticles diffusely distributed in the amorphous diamond-rich phase to form a hard and wear-resistant W2C, the coating microhardness increased significantly, the coating's strength, abrasion resistance, toughness, corrosion resistance, thermal barriers, heat fatigue resistance, and other properties significantly improved.A NIEDERHOFER et al. used physical vapor deposition technology to coat TiN system nano-coatings, the use of nanomaterials to achieve the grain ultrafine grain refinement and grain boundary strengthening, through the thin film preparation process doped with trace amounts of Si, so that the coating produces nanoscale grain refinement, so that the deposited coating has a more excellent performance, high hardness, wear resistance, has been widely used in the surface of mold parts.
Research shows that the nanocomposite brush plating technology developed on the basis of traditional brush plating, the application of nano-hard particles to the brush plating process, due to the ultra-fine nano-materials, so that the coating can have a unique performance, can have more excellent strength and hardness than the traditional materials to improve the surface performance of the product. The application of nanomaterials to the surface treatment of mold cavities can effectively enhance the thickness of the coating, improve the hardness, wear resistance, corrosion resistance, anti-fatigue ability, to ensure the stability of the full-cycle service of the mold, and extend the service life of the mold.
S136 die steel has excellent corrosion resistance, widely used in the mold industry, in order to meet the increasingly complex structure and high quality of the demand for injected products, selective laser melting (SLM) as a new manufacturing method is used for rapid manufacturing of complex geometry parts. At the same time, in order to achieve higher hardness and wear resistance and longer mold life, researchers have found that the formation of stable nanoscale microstructures in TiB2/S136 composites by SLM will help to improve the hardness and wear properties of such materials, and it was determined that the composite material performs optimally when TiB2 nanoparticles are added to S136 at a content of 0.5 wt% and has a fairly low The wear rate was determined to be optimal with the addition of 0.5 wt% of TiB2 nanoparticles to S136, as the TiB2/S136 composites showed the finest grains, and the dispersed TiB2 nanoparticles were bonded to each other in a highly homogeneous manner to form a fine, continuous, and homogeneously distributed toroidal structure, with an average thickness of 350 nm, which is comprised of thin “metal-ceramic” interfaces along the grain boundaries, contributing to The structure consists of thin “metal-ceramic” interfaces along the grain boundaries, which contributes to grain refinement and strengthening of grain boundaries.
Traditional mold surface coating technology continues to improve and optimize, constantly pursuing more refined coatings, more precise process control, more excellence in performance. Surface coating technology toward the direction of composite coating, nano-coating, automation and intelligent coating development.