Polysilazane nano composite coating and method for treating surface of mold

Abstract

The invention discloses a polysilazane nano composite coating and a method for treating the surface of a mold. The polysilazane nano composite coating comprises the following components: polysilazane resin, nano aluminum oxide, nano silicon oxide, nano boron nitride, a dispersing agent, a flatting agent, a defoaming agent and a solvent. The method comprises the following steps: spraying a polysilazane nano composite coating on the surface of a mold; the mold is placed at the temperature of 140-160 DEG C to be baked for 15-20 min, and then the mold is heated to 240-260 DEG C to be baked for 30-60 min. The problems of pollution, high cost, poor coverage, easiness in stripping and the like existing in an existing mold surface treatment technology are solved.

Description

Technical Field

[0001] This invention relates to the field of metal mold surface protection technology, specifically to a polysilazane nanocomposite coating and a method for treating the mold surface. Background Technology

[0002] Metal molds (such as tool steel, stainless steel, aluminum alloy, and magnesium alloy molds) are key tooling in modern manufacturing, and their performance and lifespan directly affect production efficiency and product quality. In processes such as plastic injection molding, magnesium alloy die casting, and semi-solid injection molding, the mold surface faces severe challenges: 1. Corrosion and high-temperature oxidation: Molten metal, semi-solid metal, mold release agents, and oxidizing atmospheres at high temperatures (>300°C). 2. Product adhesion and carbon buildup: This leads to difficulty in demolding, requiring frequent shutdowns for cleaning, affecting product surface quality and production continuity. 3. Wear and scratches: Magnesium alloy semi-solid slurry contains approximately 30-50% solid α-Mg spherical crystals. These hard solid particles act like abrasives when flowing at high speeds, causing severe abrasive wear and scratches on the mold surface, especially in narrow gaps and corners. Existing surface treatment technologies such as hard chrome plating, physical vapor deposition (PVD), and chemical vapor deposition (CVD) can solve the problem to some extent, but they have the following limitations: hard chrome plating causes environmental pollution and the coating has many microcracks; PVD / CVD equipment is expensive, has poor coverage for complex cavities, and the coating has high internal stress and is easy to peel off.

[0003] Therefore, developing a polysilazane nanocomposite coating technology that can firmly bond with various metal substrates and possesses both toughness and multifunctionality has significant industrial application value. Summary of the Invention

[0004] The purpose of this invention is to provide a polysilazane nanocomposite coating and a method for treating the surface of a mold, which solves the problems of pollution, high cost, poor coverage and easy peeling of existing mold surface treatment technologies.

[0005] To achieve the above objectives, the present invention provides a polysilazane nanocomposite coating, wherein the components of the polysilazane nanocomposite coating include polysilazane resin, nano alumina, nano silica, nano boron nitride, dispersant, leveling agent, defoamer and solvent.

[0006] Preferably, the polysilazane nanocomposite coating comprises 20-30 wt% polysilazane resin, 5-15 wt% nano alumina, 5-15 wt% nano silica, 5-15 wt% nano boron nitride, 0.1-1 wt% dispersant, 0.1-0.5 wt% leveling agent, 0.1-0.3 wt% defoamer, and the balance being solvent.

[0007] The present invention also provides a method for treating the surface of a mold using the above-mentioned polysilazane nanocomposite coating, the method comprising: 1) Spray the polysilazane nanocomposite coating onto the mold surface; 2) Bake the mold at 140-160℃ for 15-20 minutes, then increase the temperature to 240-260℃ and bake for 30-60 minutes.

[0008] Preferably, the mold is pretreated before spraying, the pretreatment including sandblasting with corundum sand, and dip coating or spraying with silane coupling agent solution.

[0009] Preferably, the particle size of the corundum sand is 150-400 mesh, and the roughness of the mold surface after sandblasting is controlled at 1.0-3.5μm.

[0010] Preferably, after dip coating or spray coating with silane coupling agent solution, the mold is dried at 80-120°C for 5-15 minutes.

[0011] Beneficial Effects: This invention provides a polysilazane nanocomposite coating, the components of which include polysilazane resin, nano-alumina, nano-silica, nano-boron nitride, dispersant, leveling agent, defoamer, and solvent. It also provides a method for treating a mold surface using the above-mentioned polysilazane nanocomposite coating, the method comprising: spraying the polysilazane nanocomposite coating onto the mold surface; baking the mold at 140-160℃ for 15-20 min, followed by baking at 240-260℃ for 30-60 min. The technical solution of this invention effectively solves the problem of universality and high adhesion of polysilazane coatings on various metal substrates (steel, aluminum, magnesium, etc.) through a two-step pretreatment method of physical roughening and chemical activation, and a specially formulated epoxy functional group silane modified underlayer. The single coating system simultaneously provides excellent wear resistance, corrosion resistance, high-temperature oxidation resistance (long-term 400°C), and durable anti-adhesion properties, reducing dependence on external release agents. The coating is dense and stable, and it bonds firmly to the substrate, which increases the service life of the mold by more than 50% under harsh working conditions, greatly reducing downtime maintenance time and mold replacement costs.

[0012] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0013] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. The following examples are for a magnesium alloy semi-solid injection mold (AZ91D).

[0014] Example 1 The mold underwent pretreatment before spraying, including sandblasting with corundum sand (180 mesh) to achieve a surface roughness of 2.8 μm. After spraying with KH-550 ethanol solution, it was dried at 80°C for 15 min. Then, a KH-550 coating containing 3% nano-SiO2 was sprayed on, with a thickness of 6 μm. The mold was then dried at 100°C for 10 min to form a chemically activated layer. A polysilazane nanocomposite coating was then sprayed onto the mold surface. The mold was baked at 150°C for 18 min, followed by baking at 250°C for 45 min. The polysilazane nanocomposite coating comprises 25wt% polysilazane resin (using Merck Durazane 1500 resin), 10wt% nano-alumina, 10wt% nano-silica, 10wt% nano-boron nitride, 0.5wt% dispersant (BYK-163), 0.3wt% leveling agent (BYK-333), 0.2wt% defoamer (BYK-055), and the balance solvent (xylene). The coating on the mold was tested; the adhesion was grade 0, the pencil hardness was 9H, the mold lifespan increased by approximately 50% compared to the untreated version, and product demolding was smooth.

[0015] Example 2 The mold underwent pretreatment before spraying, including sandblasting with corundum sand (150 mesh) to achieve a surface roughness of 1.0 μm. After spraying with KH-550 ethanol solution, it was dried at 80°C for 15 min. Then, a KH-550 coating containing 3% nano-SiO2 was sprayed on, with a thickness of 5 μm. The mold was dried at 80°C for 5 min to form a chemically activated layer. A polysilazane nanocomposite coating was then sprayed onto the mold surface. The mold was baked at 140°C for 15 min, followed by baking at 240°C for 30 min. The polysilazane nanocomposite coating comprises 20wt% polysilazane resin (using Merck Durazane 1500 resin), 5wt% nano-alumina, 5wt% nano-silica, 5wt% nano-boron nitride, 0.1wt% dispersant (BYK-163), 0.1wt% leveling agent (BYK-333), 0.1wt% defoamer (BYK-055), and the balance solvent (xylene). The coating on the mold was tested; the adhesion was grade 0, the pencil hardness was 9H, the mold lifespan increased by approximately 50% compared to the untreated version, and product demolding was smooth.

[0016] Example 3 The mold underwent pretreatment before spraying, including sandblasting with corundum sand (400 mesh) to achieve a surface roughness of 3.5 μm. After spraying with KH-550 ethanol solution, it was dried at 80°C for 15 min. Then, a KH-550 coating containing 3% nano-SiO2 was sprayed on, with a thickness of 8 μm. The mold was then dried at 120°C for 15 min to form a chemically activated layer. A polysilazane nanocomposite coating was then sprayed onto the mold surface. The mold was baked at 160°C for 20 min, followed by baking at 260°C for 60 min. The polysilazane nanocomposite coating comprises 30wt% polysilazane resin (using Merck Durazane 1500 resin), 15wt% nano-alumina, 15wt% nano-silica, 15wt% nano-boron nitride, 1wt% dispersant (BYK-163), 0.5wt% leveling agent (BYK-333), 0.3wt% defoamer (BYK-055), and the balance solvent (xylene). The coating on the mold was tested; the adhesion was grade 0, the pencil hardness was 9H, the mold life was increased by approximately 50% compared to the untreated version, and product demolding was smooth.

[0017] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0018] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0019] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A polysilazane nanocomposite coating, characterized in that, The components of the polysilazane nanocomposite coating include polysilazane resin, nano alumina, nano silica, nano boron nitride, dispersant, leveling agent, defoamer, and solvent.

2. The polysilazane nanocomposite coating according to claim 1, characterized in that, The polysilazane nanocomposite coating comprises 20-30 wt% polysilazane resin, 5-15 wt% nano alumina, 5-15 wt% nano silica, 5-15 wt% nano boron nitride, 0.1-1 wt% dispersant, 0.1-0.5 wt% leveling agent, 0.1-0.3 wt% defoamer, and the balance being solvent.

3. A method for treating the surface of a mold using the polysilazane nanocomposite coating as described in claim 1 or 2, characterized in that, The method includes: 1) Spray the polysilazane nanocomposite coating onto the mold surface; 2) Bake the mold at 140-160℃ for 15-20 minutes, then increase the temperature to 240-260℃ and bake for 30-60 minutes.

4. The method according to claim 3, characterized in that, The mold is pretreated before spraying. The pretreatment includes sandblasting with corundum sand and dipping or spraying with silane coupling agent solution.

5. The method according to claim 4, characterized in that, The particle size of corundum sand is 150-400 mesh, and the surface roughness of the mold is controlled at 1.0-3.5μm after sandblasting.

6. The method according to claim 4, characterized in that, After dip coating or spraying with silane coupling agent solution, dry the mold at 80-120℃ for 5-15 minutes.