Mold surface enhancement technology: plasma-chemical treatment

1 plasma-chemical treatment

    The fastest growing, most widely used industrial heat treatment of plasma is plasma-chemical treatment. Compared with conventional chemical treatment, plasma-chemical treatment with high-quality, high efficiency, low consumption, clean, pollution-free and so on. However, this technology for large quantities of small molds, and other small parts (such as bolts, nuts, chains, etc.), installed furnace trouble, layer quality is not easy to control. Moreover, the same furnace mix of different shapes, sizes of the workpiece, the workpiece is not easy to uniformly control the temperature.

    1.1 Ion carburizing

    Ion carburizing, also known as glow carburizing [l0-11]. Carburizing is cheap, has good formability and ductility of low carbon steel or low carbon alloy steel parent material in an atmosphere of carbon-based heating, so that carbon into the base material to form tough, wear-resistant surface of a heat treatment method. Ion carburizing is that carbon is a hydrocarbon gas plasma in a vacuum, by DC glow discharge ionization obtained, the principle is similar to ion nitriding.

 

    In China, plasma carburizing process has been successfully used in automotive, aerospace, nuclear industry such as mold. Ion carburizing technology diffusion layer is the key to quality control and equipment design. Plasma carburizing, the carbon flux and by adjusting the time to control the carburization pre-mold surface carbon content. Carbon flux is the gas composition, pressure, gas flow, ion current density and the carburizing temperature. In industrial production, plasma carburizing, you can use the spread and transmission of carbon mathematical model, the current density sensor through the entire process by computer process control, to obtain a predetermined surface of the carbon content, carbon distribution and penetration depth. However, the high temperature plasma carburizing process (850 ~ 980 ℃), requires power supply power, prone to glow discharge into arc discharge phenomenon, making the process unstable, more complex equipment. At present, widely used on industrial molds and vacuum gas carburizing carburizing process maturity, quality and stability, to better meet the needs of industrial molds. Compared with the conventional carburizing, ion carburizing has the following advantages: carburizing, high efficiency, good surface quality, layer distribution, deformation, environmental pollution, easy to automate process control, deep blind hole can also handle other . In the mold industry, ion carburizing in die and plastic mold used more often. Currently, surface hardening, 80% are carburizing. Thus, ion carburizing has broad prospects for development.

    1.2 ion-nitriding

    Ion nitriding is the most widely used in industry, most mature plasma heat treatment [1-3]. The process is easy by adjusting the process parameters (such as voltage, current, furnace gas pressure, temperature, time, and working gas composition, etc.) to obtain pure diffusion layer, single-phase compound layer. Ion nitriding technique is how its key features, combined with the mold-related conditions of service, a reasonable choice of process parameters, and then get the best penetration layer.

    1.3 Ion Carbon - nitriding

    Nitrogen ion carburizing furnace gas technology is to rely on active components C3H8 and NH3 decomposition on steel, precipitation of active C and N atoms are absorbed to the substrate surface to achieve the internal diffusion [2,4], it is also known as ion soft-nitrogen technology, from the salt-bath soft nitriding gas evolved. Nitrogen ion carburizing and ion nitriding operation method is basically the same, but the working gas composition is different, the cooling conditions in addition to the slow cooling in a vacuum, but also for oil quenching or high-pressure gas quenching. Ion-carbon-nitriding time is short, effective, available thicker compound layer, with excellent abrasion resistance, bonding and anti-fatigue properties. Compared with the traditional process, the mold used in carbon-ion-nitriding technology not only has a diffusion layer of good quality, easy to control with the advantages of the composition, and efficient, clean, energy-saving. The process has a strong market competitiveness.

  1.4 Ion boronizing

 

    Boride is a very effective surface hardening process. Boronizing metal parts, the surface of the boride and boron compounds such as high hardness, infiltration boron steel in hardness, wear resistance, heat resistance, corrosion resistance than carburizing or nitriding on steel high [1 , 4]. Therefore, in the mold surface hardening, the penetration of boron plays an important role. Boronizing many ways, the conventional method of gas, liquid, solid and electrolytic boron penetration. Boride ion diffusion layer materials are uniform, rapid infiltration rate, infiltration without cleaning up after the work piece, etc., is a promising technology.

 

    1.5 plasma surface alloying

 

    Mold surface alloying refers to a certain temperature and vacuum conditions, the reduction of the active metal atoms, or ionized, sputtered out of the metal atoms diffuse into the mold steel substrate surface to form alloy diffusion layer, thus changing the surface chemical composition, structure and properties method. Mold surface alloying technology are areas of chemical heat treatment of steel, in essence, through high-temperature diffusion, the chromium, vanadium, titanium, tungsten, molybdenum, niobium, cobalt, nickel, aluminum and other active atoms in the mold surface layer of solid solution or carbide infiltration organization, its high hardness, good wear resistance, and has good resistance to oxidation and corrosion resistance, greatly improving the performance and service life of the mold surface [12].