In terms of material selection
Difficult to find suitable materials: To achieve high hardness requirements, it is necessary to select basic materials with high hardness characteristics. For example, some ceramic materials (such as titanium nitride, tungsten carbide, etc.) may have high hardness, but their toughness and adhesion to the substrate may not be well balanced. Finding materials that are suitable for comprehensive performance is a challenge in itself. Moreover, different application scenarios have additional requirements for properties beyond hardness, such as high temperature resistance, corrosion resistance, etc., further limiting the range of material choices.
Material purity control: Even if a suitable material is determined, it is not easy to ensure its purity. The presence of impurities may greatly affect the final hardness and other properties of the coating. For example, trace impurities may become stress concentration points, leading to cracks or even peeling of the coating during use. Therefore, there are strict requirements for purity during material preparation and selection.
In terms of preparation process
Precise control of process parameters: Whether using common coating preparation methods such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), subtle changes in process parameters can have a significant impact on coating hardness. For example, parameters such as sputtering power, deposition time, and gas flow rate in PVD need to be precisely controlled in order to achieve ordered atomic arrangement and good crystallization of the coating, thereby achieving high hardness. Accurately grasping these parameters and maintaining stability within an appropriate range is a test of technical level.
Uniformity guarantee: It is difficult to make the coating evenly distributed on the surface of the substrate, especially for workpieces with complex shapes, which can easily lead to uneven coating thickness and hardness in some areas. Special process design and operational skills are required to ensure uniform coating coverage and hardness on substrates with complex structures such as holes, gaps, and curved surfaces. Otherwise, significant differences in wear and tear in different parts during use can affect overall performance.
In terms of coating substrate bonding
Enhancement of bonding strength: If the high hardness coating cannot be firmly bonded to the substrate, it is easy to peel off from the substrate when subjected to external forces, and it cannot play its due role. To achieve good bonding, it is necessary to consider factors such as the pre-treatment of the substrate, the matching of thermal expansion coefficients between the coating and the substrate, etc., in order to form strong chemical bonds, mechanical interlocking, and other bonding forms between the coating and the substrate. This often requires repeated experimentation and process optimization.
Internal stress treatment: During the coating preparation process, internal stress is easily generated due to factors such as material deposition and temperature changes, and the internal stress problem of high hardness coatings may be more prominent. Excessive internal stress can weaken the adhesion between the coating and the substrate, and may directly cause defects such as cracking in the coating itself. Effective control and elimination of internal stress require high requirements for process control and post-treatment.
In terms of testing and quality control
Accurate measurement of hardness: For high hardness coatings, it is crucial to choose the appropriate hardness measurement method and equipment. Different measurement methods (such as Rockwell hardness, Vickers hardness, nanoindentation, etc.) have their own applicable ranges and measurement errors. Accurately measuring the true hardness of the coating is not easy, and when the coating is thin, the measurement results are easily affected by the substrate. How to accurately obtain the coating's own hardness index for quality control is a difficult problem.
Quality stability assurance: To ensure that each batch of high hardness coatings produced can stably achieve the expected hardness and other performance indicators, it is necessary to establish a sound quality control system, strictly control multiple links from raw material inspection, process monitoring to finished product testing, etc. Any fluctuation in any link may lead to uneven coating quality.

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