Mar 09,2026
Pyramid of Mold Surface Processing Techniques: From Chrom-plated to Diamond-like Coating
Pyramid of Mold Surface Processing Techniques: From Chrom-plated to Diamond-like Coating
Surface treatment, PVD coating, CVD coating, DLC coating, Chrome plating
The working surface of the mold is the “front line” directly in contact with high temperature, high pressure, and high friction component materials. The underlying steel provides the overall strength and resilience of the mold, while surface processing gives it a special “armor” against wear, corrosion, adhesion, and fatigue. From traditional chromium coating to modern PVD coating, CVD coating, and even diamond-like coating, the development of surface processing technologies constitutes a hierarchy of performance-enhancing technologies, each with its own unique advantages and applications.
Tower: Traditional surface treatment techniques – chromium coating and nitrogenation.
Located at the base of the pyramid is a long-standing but still widely used treatment of hardened chromium and nitrogenation. Hardened chromium provides high hardness and excellent corrosion resistance by electrically depositing a layer of chromium metal on the surface of the mold. Its advantages lie in its mature process, low cost, and coating thickness (up to dozens of microns), suitable for repairing worn mold sizes. However, the chromium coating has micro-cracks, limited hardness (approximately HV800-1000), and is prone to softening at high temperatures, posing environmental challenges. Nitrification (gas nitrification, ion nitrification) is the formation of a nitrification layer by infiltrating nitrogen atoms into the surface of the mold, significantly improving surface hardness and fatigue resistance. It is characterized by low treatment temperatures (500–570°C), minimal deformation, and strong binding to the substrate with no peeling risk. It is widely applied in situations that require anti-stick wear, such as aluminum cast mold and plastic mold. However, the nitrification layer is thinner (typically 0.1–0.5 mm), and the hardness increase is limited (approximately HV1000–1200).
Tower body: PVD coating technology – a revolution in hard coating.
The emergence of Physical Vapour Deposition (PVD) technology, which raises the hardness of the mold surface by an order of magnitude, is at the heart of modern coating technology. PVD, which vaporizes solid materials and deposits them on the mold surface in a vacuum through physical methods such as evaporation and splattering, forms an extremely thin (2-5 μm) but extremely hard ceramic coating. The most classic TiN (Nitro-Titanium) coating, with its signature gold color and hardness of about HV2300, became the first industrial standard. Subsequently, more advanced TiCN (Carbon-Nitro-Titanium) and TiAlN (Nitro-Aluminum-Titanium) gradually became mainstream. TiCN, by introducing carbon elements, increases hardness to about HV3000, and has lower friction coefficients. TiAlN, by forming a dense layer of aluminum oxide at high temperatures, exhibits excellent red hardness and antioxidant properties, becoming a sharp tool for dry cutting and high-speed processing, with thermal hardness that can be maintained above 800°C. The advantages of PVD coatings are that they have low sedimentation temperatures (usually below 500°C), have no impact on molding substrate performance, and have dense coatings with good binding strength, making them the preferred choice for precision cut, stretch, and injection molding.
Pinnacle: CVD and diamond-like coating – the pinnacle of extreme performance.
At the apex of the pyramid are the highest levels of Chemical vapor deposition (CVD) and diamond-like (DLC) coatings. Chemical vapor deposition (CVD) deposits on the surface of the mold through chemical reactions, typically represented by multi-layered composite coatings of TiC (titanium carbonide) and Al2O3 (aluminum oxide). The CVD coatings have extremely strong binding force, can deposit thicker coatings (up to 10–20 μm), are extremely hard and have excellent abrasion resistance. However, their deposition temperature of up to 800–1000°C can cause mold substrate deforestation, limiting their application on delicate and complex molds, mainly used for hard alloy blades and molding parts that require extreme abrasion resistance. The diamond-like coating is the pearl of the pyramid. DLC is a non-crystalline carbon material with a hardness close to that of natural diamonds (up to HV5000-8000), while having an extremely low friction coefficient (low to 0.1 below) and excellent chemical inertia. It can be as hard and abrasive as diamonds, but can also self-oil like graphite. It is the ultimate coating for processing colored metals (such as aluminum, copper alloys) and adhesive materials, and can effectively solve the problems of “bite” and “stack tumor.” However, the high internal tension of DLC coating and its binding strength to steel substrates are technical challenges and expensive. Currently, it is mainly applied to precision casts and critical components with extreme performance requirements.
Scientific Decisions for Coating Types: “Layering” by “Material.”
Faced with this technological pyramid, how to choose the most appropriate coating for a specific mold requires a deep analysis of the artifact materials, failure patterns, and process conditions. Molds made of pressed stainless steel or high-strength steel require a high-hardness, high-abrasion-resistant TiAlN or AlCrN coating. Molds made of stretch aluminum alloys require a low-friction, adhesion-resistant DLC or special carbon coating. Molds made of infused fiberglass plastics require a strong binding, granular abrasion-resistant TiCN or multi-layer composite coating. Molds that process corrosive materials need to consider CrN coatings with corrosion-resistant properties. A professional mold supplier should have a deep understanding of coating technology and the ability to work with top coating centers. They should be able to recommend the most scientific and cost-effective coating solutions based on the specific needs of their customers. They should be able to put the most appropriate “armor” on the mold, thereby winning a double victory in performance and longevity in fierce market competition.
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