PVD (Physical Vapor Deposition) composite coated cooker and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out surface cleaning and activating treatment on a metal cooker base body, putting the cooker into PVD coating equipment, vacuumizing, configuring a titanium target, a multi-component composite target and an oxide target, cleaning the surface of the cooker by adopting ion bombardment, depositing a titanium transition layer with the thickness of 0.1-0.5 mu m, and carrying out vacuum treatment to obtain the PVD composite coating cooker. The thickness of the deposited copper-aluminum-silicon-chromium carbide composite functional layer is 4.5-5.5 microns, the thickness of the deposited oxide surface layer is 0.2-0.8 microns, and furnace cooling is carried out after film plating is completed. The three-layer gradient structure design is adopted, the titanium transition layer and the base body form metallurgical bonding, the copper-aluminum-silicon-chromium carbide composite functional layer provides hydrophobic and oleophylic performance, the oxide surface layer blocks oxygen and nitrogen diffusion, and the comprehensive performance of being high in film layer bonding force, resistant to high temperature and lasting and non-sticky is achieved.

Description

Technical Field

[0001] This invention relates to the field of cookware surface treatment technology, specifically to physical vapor deposition (PVD) composite coating technology, and more specifically, to a cookware and its preparation method that uses a multi-power source synergistic process to prepare a nitrogen-free carbide + oxide three-layer gradient composite coating. The coating system of this invention is completely different from existing chromium-based paint and nitride / carbonitride coating systems, and is suitable for Chinese high-temperature stir-fry cooking scenarios, possessing comprehensive properties such as strong adhesion, high temperature resistance, long-lasting non-stick properties, and hydrophobic and oleophilic properties. Background Technology

[0002] Cookware is a basic tool for daily cooking, widely used in home kitchens, the catering industry, and other fields. With increasing demands for healthy eating and convenient cooking, cookware surface treatment technology has become a key factor influencing product performance. An ideal cookware surface should possess comprehensive properties such as non-stickness, easy cleaning, high-temperature resistance, and wear resistance to meet the needs of modern cooking.

[0003] Traditional non-stick coatings for cookware primarily use polytetrafluoroethylene (PTFE) or silicon-containing ceramic coatings, which are applied to the cookware surface via spraying or dipping to form an organic coating. While these coatings offer good non-stick properties, they suffer from a relatively low temperature limit, typically not exceeding 260°C. Under high-temperature cooking conditions such as dry burning or stir-frying, the coating is prone to softening and decomposition, leading to a decrease or even failure of its non-stick properties. Furthermore, the PTFE coating relies mainly on physical adsorption for bonding with the metal substrate, resulting in limited bonding strength. Over long-term use, issues such as coating peeling and blistering can occur, affecting the lifespan of the cookware and compromising food safety.

[0004] To overcome the limitations of organic coatings, physical vapor deposition (PVD) technology has been increasingly applied to cookware surface treatment. Several PVD-coated cookware products have been disclosed in existing technologies. Among them, US6197438B1 discloses a tableware coating technology using a chromium / chromium nitride dual-layer as a primer, superimposed with nitride / diamond-like ceramic layers such as TiN / ZrN / diamond. CN102378830A discloses a copper tableware coating technology using a cathode arc + sputtering composite deposition of a metal substrate, followed by superimposed with alternating nitride / carbonitride layers such as (Ti,Al,Cr)N / CrN. These two existing technologies represent the mainstream solutions for PVD-coated cookware, but they still suffer from many unresolved technical defects.

[0005] 1. The core coating system has high temperature stability defects: The above-mentioned existing technologies all use nitrides / carbonitrides as the core functional layer. Nitrides are prone to further oxidation or nitriding reactions with oxygen and nitrogen atoms in high temperature environment, which leads to the deterioration of film composition and microstructure. After long-term high temperature use, the wear resistance and non-stick performance are greatly reduced, making it difficult to adapt to the cooking needs of Chinese high-temperature stir-frying. 2. Defects in the bonding strength and process of the substrate / primer structure design: US6197438B1 uses chromium / chromium nitride as a primer, which only has physical / chemical bonding with the substrate, resulting in limited stress buffering capacity. In addition, some solutions require plasma spraying of a chromium layer onto the substrate, which is complex and costly. CN102378830A uses a cathode arc + sputtering composite deposition substrate, which requires precise control of the synergistic parameters of the two processes. The process window is narrow, making mass production difficult. 3. The target material and functional design are simple and cannot take into account comprehensive performance: Existing technologies all use a single metal target (Ti / Cr / Zr) or a binary / ternary nitride target. The coating function is only focused on wear resistance and corrosion resistance. The surface energy is high, and it is difficult to achieve both hydrophobic and oleophilic properties at the same time. Food is easy to adhere to, and the non-stick performance is not durable. 4. High process complexity and high production cost: The deposition of nitride / carbonitride systems must be carried out in a nitrogen atmosphere throughout the process, which places strict requirements on the control of equipment vacuum and gas ratio, increasing the complexity of the process and the production cost.

[0006] In addition, the upper limit of the temperature resistance of existing nitride-coated cookware is generally no more than 400℃, and some solutions contain diamond / diamond-like coatings, which have the problem of high coating brittleness and easy cracking, further limiting their practical application scenarios.

[0007] Therefore, there is an urgent need for a new cookware surface treatment technology that completely avoids the existing chromium-based paint and nitride / carbonitride technology routes. While maintaining the high hardness and strong adhesion of the film layer, it should further improve the high temperature resistance and high temperature stability, achieve synergistic optimization of hydrophobic and oleophilic properties, and at the same time simplify the process and reduce production costs to meet the comprehensive performance requirements of modern cookware for durable non-stick, high temperature resistance, long life and health and environmental protection. Summary of the Invention

[0008] The purpose of this invention is to provide a PVD composite coated cookware and its preparation method, which completely avoids the technical route of existing chromium base paint and nitride / carbonitride coating systems. It solves the technical problems of poor high-temperature resistance of non-stick coatings in existing cookware, insufficient film-substrate adhesion and easy peeling, easy oxidation and nitridation of nitride systems at high temperatures, single target material function, and complex and costly processes. It achieves comprehensive performance of strong film adhesion, high temperature resistance, long-lasting non-stick, hydrophobic and oleophilic properties, and health and environmental protection.

[0009] Technical solution To achieve the above objectives, the present invention provides a method for preparing a PVD composite coated cookware, comprising the following steps: S1. Perform surface cleaning and activation treatment on the metal cookware substrate, wherein the metal cookware substrate is a conventional metal substrate that has not undergone plasma spraying chromium layer treatment; S2. Place the cleaned cookware into the PVD coating equipment and evacuate to a vacuum level ≤5×10⁻⁶. - ³Pa, the PVD coating equipment is equipped with 2 pure titanium targets, 6 copper-aluminum-silicon-chromium carbide quaternary composite carbide targets and 2 oxide targets. Argon gas is used as the working gas throughout the process, and no nitrogen gas is introduced, so no nitride / carbonitride coating is deposited. S3. Turn on the bias power supply to -800V to -1200V, adopt a pulse mode with a duty cycle of 20% and turn on the multi-arc power supply to generate argon ions and metal ions to bombard the surface of the cookware for plasma cleaning. The cleaning process does not involve the combined deposition of cathode arc and sputtering processes. After cleaning, reduce the bias voltage to -400V to -500V, adjust the duty cycle to 40%-50%, and continue to work the multi-arc power supply to bombard the pure titanium target, depositing a pure titanium transition layer on the substrate surface. There is no chromium metal layer or chromium nitride layer deposition. The titanium transition layer is not nitrided and has a thickness of 0.1–0.5μm. The deposition process is pure multi-arc deposition without sputtering process. S4. Turn off the multi-arc bias and turn on the intermediate frequency power supply to bombard the copper-aluminum-silicon-chromium carbide quaternary composite carbide target to deposit a copper-aluminum-silicon-chromium carbide composite functional layer on the titanium transition layer. The composite functional layer is a pure carbide system without nitrogen doping. The thickness of the composite functional layer is 4.5–5.5 μm. The deposition process is pure intermediate frequency sputtering without the participation of cathode arc process. S5. Turn off the bias voltage and intermediate frequency power supply, turn on the RF power supply or pulsed DC power supply to bombard the oxide target, deposit an oxide surface layer on the surface of the composite functional layer, without diamond or diamond-like coating deposition, the oxide surface layer thickness is 0.2–0.8μm, the deposition process is pure RF / pulsed DC sputtering, without the participation of cathode arc or multi-arc processes. S6. After coating is completed, the furnace is cooled to room temperature.

[0010] Further, in step S3, the argon gas with a purity of 99.999% is introduced, and the plasma cleaning parameters are: bias voltage -800 to -1200V, argon gas flow rate 50–100sccm, working pressure 0.5–1.0Pa, and cleaning time 10–20min; the titanium transition layer deposition parameters are: bias voltage -400 to -500V, multi-arc current 60–100A, argon gas flow rate 20–50sccm, working pressure 0.3–0.8Pa, and deposition temperature 200–300℃.

[0011] Furthermore, the copper-aluminum-silicon-chromium carbide quaternary composite carbide target is prepared by powder metallurgy sintering. In step S4, the intermediate frequency power supply has a frequency of 20–40 kHz, a power density of 5–10 W / cm², an argon flow rate of 30–60 sccm, a working pressure of 0.4–0.9 Pa, and a deposition temperature of 250–350 °C.

[0012] Furthermore, the oxide target is a silicon dioxide target. In step S5, the radio frequency power supply frequency is 13.56 MHz, the power is 500–1500 W, the argon flow rate is 10–30 sccm, the working pressure is 0.2–0.6 Pa, and the deposition temperature is 200–280℃.

[0013] Furthermore, in step S1, the surface cleaning and activation treatment is a three-stage cleaning process: ultrasonic alkaline washing → acid washing and activation → deionized water rinsing → drying, without any other surface metal layer pretreatment.

[0014] This invention also provides a PVD composite coated cookware, prepared by the above-described method, comprising, from the inside out: a metal cookware substrate, which is a conventional metal substrate without plasma spraying of a chromium layer and without chromium-free base paint treatment; a pure titanium transition layer, deposited on the surface of the metal cookware substrate to form a metallurgical bond with the substrate, with a chromium-free / chromium nitride underlayer and a cathode arc + sputtering composite substrate structure, the titanium transition layer having a thickness of 0.1–0.5 μm; and a copper-aluminum-silicon-chromium carbide composite functional layer, deposited on the titanium transition layer, the composite functional layer being pure... The carbide system, without nitrogen doping, is composed of 0.5–5% copper, 3–20% aluminum, 10–25% silicon, and 45–75% chromium carbide by weight, preferably 1%–3% copper, 5%–15% aluminum, 15%–20% silicon, and 50%–70% chromium carbide by weight, with a composite functional layer thickness of 4.5–5.5 μm; the oxide surface layer, deposited on the surface of the composite functional layer, is a dense silicon dioxide barrier layer without diamond or diamond-like coating, with an oxide surface layer thickness of 0.2–0.8 μm.

[0015] Furthermore, the total thickness of the titanium transition layer, the copper-aluminum-silicon-chromium carbide composite functional layer, and the oxide surface layer is 3–6.8 μm, preferably 5–6 μm.

[0016] This invention completely avoids the technical path structure and multi-source independent deposition process of existing chromium-based paints, nitrides / carbonitrides, etc. Compared with existing technologies such as US6197438B1 and CN102378830A, it adopts a nitrogen-free carbide + oxide three-layer ladder, which has the following significant advantages: 1. Strong film-substrate adhesion and excellent stress buffering capacity: The pure titanium transition layer forms a metallurgical bond with the metal substrate. The interfacial bonding energy is much higher than that of the physical / chemical bonding of existing chromium-based paints. It is free of chromium / chromium nitride layers and cathode arc + sputtering composite substrate structure. The thermal expansion coefficient of titanium is between that of the metal substrate and the subsequent composite functional layer, which plays an efficient gradient transition role and buffers the interfacial stress caused by the difference in thermal expansion coefficient. The film-substrate adhesion reaches the 0-level standard of the cross-cut adhesion test, with no peeling or cracking. The adhesion is improved by more than 50% compared with the existing nitride system. 2. The core coating system exhibits excellent high-temperature stability and a significantly improved upper limit for high-temperature resistance: It adopts a nitrogen-free system of pure carbides (copper, aluminum, silicon, chromium carbide) + oxides (silicon dioxide), with only argon gas introduced throughout the process, and no nitrogen gas introduced or nitrogen element doping. This fundamentally avoids the degradation problems of high-temperature oxidation and nitriding in existing nitride systems. Furthermore, a highly dense barrier layer is formed on the surface of silicon dioxide, effectively blocking the diffusion of oxygen and nitrogen atoms from the environment into the interior, protecting the composite functional layer from changes in composition and structure at high temperatures. The high-temperature resistance performance reaches 500℃ dry burning for 30 minutes without discoloration or peeling, which is ≥100℃ higher than the upper limit of high-temperature resistance of existing nitride systems. 3. Hydrophobic and oleophilic dual properties, excellent long-lasting non-stick performance: The copper-aluminum-silicon-chromium carbide quaternary composite carbide functional layer is an independently developed innovative design, which is different from the existing single metal / nitride target material. Among them, chromium carbide forms a high-hardness and wear-resistant skeleton, copper provides self-lubricating properties, aluminum enhances the affinity of oil and grease, and silicon constructs a low surface energy hydrophobic structure. The four components work together to achieve the dual properties of hydrophobic and oleophilic properties of "quickly spreading oil film and repelling water and soup". The surface hardness reaches HV1900, which is 12%-27% higher than the existing nitride system. After 100 egg frying tests, the non-stick performance decreases by ≤10%, and the service life is increased by more than 1 times. 4. Simplified process flow, reduced production costs, and suitability for mass production: The nitrogen atmosphere requirement of existing nitride systems is eliminated, and only argon is used as the working gas throughout the process. There is no need to precisely control the gas ratio, which reduces the equipment control requirements. Moreover, each film layer adopts independent deposition by multiple power sources (pure multi-arc, pure medium frequency sputtering, pure radio frequency / pulse DC sputtering), and there is no cathode arc + sputtering composite deposition process. The process window is wide, and the film thickness uniformity is within ±5%, which greatly simplifies the process flow and reduces the production and manufacturing costs. 5. Healthy and environmentally friendly, meeting food contact safety standards: This invention is a carbide + oxide system that is free of fluorine, nitrogen, and heavy metal doping. It does not have the risk of high-temperature decomposition of PTFE organic coatings, nor the elemental degradation and precipitation problem of nitrogen systems. High-temperature precipitation tests show that no harmful substances such as fluorides and heavy metals are released, fully meeting the safety standards for food contact materials. 6. Eliminating brittle coatings and complex substrate pretreatment, making it more practical: This invention has no brittle coatings such as diamond or diamond-like materials, and the film has excellent toughness, making it less prone to cracking and flaking; moreover, the substrate is a conventional metal substrate, without plasma-sprayed chromium layer or additional metal substrate pretreatment, making it compatible with conventional cookware substrates such as 304 stainless steel and aluminum, with a wide range of applications and easy to promote and apply in industrial applications. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow for the cookware preparation method of the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The terms used in the following embodiments are defined as follows: Film adhesion is evaluated using the cross-cut adhesion test (GB / T 9286-2021), with grade 0 indicating no peeling, grade 1 indicating slight edge peeling (less than 5%), and grade 2 indicating edge peeling (5%–15%); surface hardness is determined using the Vickers hardness test (GB / T4340.1-2009), with units of HV; high-temperature resistance is evaluated by observing film discoloration and peeling after dry burning at 500℃ for 30 minutes; persistent non-stick properties are evaluated by measuring the non-stick performance decay rate after 100 egg-frying tests; safety is evaluated by high-temperature precipitate detection (detection of fluoride and heavy metal precipitates after heating at 500℃ for 30 minutes).

[0019] Example: Please refer to Figure 1 A method for preparing a PVD composite coated cookware includes the following steps: S1. Perform surface cleaning and activation treatment on the metal cookware substrate. The metal cookware substrate is a metal substrate that has not undergone plasma spraying chromium layer treatment, such as 304 stainless steel, aluminum and other conventional cookware substrates. In step S1, the surface cleaning and activation treatment is a three-stage cleaning process: ultrasonic alkaline washing → acid washing and activation → deionized water rinsing → drying. S2. Place the cleaned cookware into the PVD coating equipment and evacuate to a vacuum level ≤5×10⁻⁶. - ³Pa, the PVD coating equipment is equipped with 2 pure titanium targets, 6 copper-aluminum-silicon-chromium carbide quaternary composite carbide targets and 2 oxide targets, and only argon gas is introduced as the working gas throughout the process. S3. Turn on the bias power supply to -800V to -1200V, using a pulse mode with a 20% duty cycle and a multi-arc power supply to generate argon ions and metal ions to bombard the cookware surface for plasma cleaning. After cleaning, reduce the bias voltage to -400V to -500V, adjust the duty cycle to 40%-50%, and continue bombarding the pure titanium target with the multi-arc power supply to deposit a pure titanium transition layer on the substrate surface. This layer is free of chromium metal layers and chromium nitride layers, and the titanium transition layer is unnitrided, with a thickness of 0.1–0.5 μm. In step S3, argon gas with a purity of 99.999% is introduced, and a high bias voltage multi-arc power supply is used to perform plasma cleaning on the cookware surface. The cleaning parameters are: bias voltage -800V to -1200V. V, argon flow rate 50–100 sccm, working pressure 0.5–1.0 Pa, cleaning time 10–20 min, cleaning process without cathode arc and sputtering process combined deposition; in step S3, the titanium transition layer deposition parameters are: bias voltage -400 to -500 V, multi-arc current 60–100 A, argon flow rate 20–50 sccm, working pressure 0.3–0.8 Pa, deposition temperature 200–300℃, the deposition process is pure multi-arc deposition, without sputtering process involved; S4. Turn off the multi-arc bias and turn on the intermediate frequency power supply to bombard the copper-aluminum-silicon-chromium carbide quaternary composite carbide target, depositing a copper-aluminum-silicon-chromium carbide composite functional layer on the titanium transition layer. This composite functional layer is a pure carbide system, and its thickness is 4.5–5.5 μm. The copper-aluminum-silicon-chromium carbide quaternary composite carbide target is prepared by powder metallurgy sintering. In step S4, the intermediate frequency power supply frequency is 20–40 kHz, and the power density is [not specified]. 5–10 W / cm², argon flow rate 30–60 sccm, working pressure 0.4–0.9 Pa, deposition temperature 250–350℃, deposition process is pure medium frequency sputtering, without cathode arc process; S5. Turn on the radio frequency power supply or pulsed DC power supply to bombard the oxide target and deposit an oxide surface layer on the surface of the composite functional layer. The thickness of the oxide surface layer is 0.2–0.8 μm. In step S5, the oxide target is a silicon dioxide target, the radio frequency power supply frequency is 13.56 MHz, the power is 500–1500 W, the argon flow rate is 10–30 sccm, the working pressure is 0.2–0.6 Pa, the deposition temperature is 200–280℃, and the deposition process is pure radio frequency / pulsed DC sputtering without the participation of cathode arc or multi-arc processes.

[0020] S6. After coating is completed, the furnace is cooled to room temperature.

[0021] A PVD composite coated cookware, prepared by the above-described preparation method, comprising: The metal cookware substrate is a metal substrate that has not undergone plasma spraying of a chromium layer or chromium-free base paint treatment; A pure titanium transition layer is deposited on the inner surface of the metal cookware substrate, forming a metallurgical bond with the substrate. It has a chromium-free / chromium nitride-free underlayer and a cathode arc + sputtering composite substrate structure. The thickness of the titanium transition layer is 0.1–0.5 μm. A copper-aluminum-silicon-chromium carbide composite functional layer is deposited on a titanium transition layer. This composite functional layer is a pure carbide system without nitrogen doping and is composed of 0.5–5% copper, 3–20% aluminum, 10–25% silicon, and 45–75% chromium carbide by weight. The thickness of the composite functional layer is 4.5–5.5 μm; preferably, it is composed of 1%–3% copper, 5%–15% aluminum, 15%–20% silicon, and 50%–70% chromium carbide by weight. The oxide surface layer, deposited on the surface of the composite functional layer, is a dense silica barrier layer without diamond or diamond-like coating. The thickness of the oxide surface layer is 0.2–0.8 μm.

[0022] In one embodiment, the total thickness of the titanium transition layer, the copper-aluminum-silicon-chromium carbide composite functional layer, and the oxide surface layer is 3–6.8 μm, preferably 5–6 μm.

[0023] The preparation process of this invention is illustrated in detail below through examples. Example 1 A method for preparing a PVD composite coated cookware includes the following steps: S1. Substrate Pretreatment: A 304 stainless steel wok was selected as the substrate for the metal cookware. The substrate is conventional cold-rolled polished austenitic stainless steel without plasma-sprayed chromium coating. A three-stage cleaning process was used for surface cleaning and activation: First, the wok was immersed in an ultrasonic cleaning tank with a 5% sodium hydroxide aqueous solution at 60°C and an ultrasonic frequency of 40 kHz for 15 minutes to remove surface oil and organic contaminants. After cleaning, it was rinsed three times with deionized water for 2 minutes each time. Then, the wok was immersed in an acid pickling tank with a 10% nitric acid aqueous solution at 25°C for 5 minutes to remove surface oxide scale and activate the surface. After acid pickling, it was rinsed five times with deionized water for 2 minutes each time until the surface pH was neutral. Finally, the wok was placed in an oven at 120°C for 30 minutes to obtain a clean and activated stainless steel substrate surface. S2. Vacuum Loading: Place the pre-treated wok into the coating chamber of the rotary PVD coating equipment. The coating equipment is a planetary rotating fixture. The wok is fixed on the fixture, which can both revolve around its central axis and rotate around its own axis. This dual rotational motion ensures uniform film thickness. The coating chamber is equipped with the following targets: 2 pure titanium targets, 99.99% purity, symmetrically arranged on both sides of the lower part of the chamber; 6 copper-aluminum-silicon-chromium carbide quaternary composite carbide targets, prepared by powder metallurgy sintering process, with a composition of 2% copper, 10% aluminum, 18% silicon, and 70% chromium carbide (mass percentage), staggered in the middle of the chamber; and 2 silicon dioxide targets, 99.9% purity, symmetrically arranged at the top of the chamber. Close the chamber door and start the vacuum pump system to evacuate to a basic vacuum level of 3×10⁻⁶. - ³ Pa, only argon gas is prepared to be introduced throughout the process, with no nitrogen gas introduced; S3. Ion Cleaning + Titanium Transition Layer Deposition: Argon gas with a purity of 99.999% is introduced, and the argon gas flow rate is controlled at 80 sccm using a mass flow meter. The working pressure in the chamber is stabilized at 0.8 Pa. A multi-arc ion source is started for plasma cleaning. The multi-arc ion source power is 5 kW. A negative bias voltage of -1000 V is applied to the wok fixture. The bias power supply is a pulsed DC power supply with a duty cycle of 20%. High-energy argon ions bombard the wok surface for 15 minutes to remove nanoscale contaminants, adsorbed gases, and oxide layers. The cleaning process involves a combination of cathode arc and sputtering processes. After plasma cleaning, the bias voltage is reduced to -300 V, the duty cycle is adjusted to 45%, and the multi-arc power supply continues to bombard the pure titanium target. A pure multi-arc deposition of the titanium transition layer is performed. The argon gas flow rate is 30 sccm, the working pressure is 0.5 Pa, the deposition temperature is 250℃, and the deposition time is 8 minutes. A pure titanium transition layer with a thickness of 0.3 μm is obtained. No chromium metal layer or chromium nitride layer is deposited, and the titanium transition layer is not nitrided. S4. Deposition of composite functional layer: The multi-arc power supply is continuously turned on, the pure titanium target heating power supply is turned off, the multi-arc bias voltage is turned off, and the medium-frequency magnetron sputtering power supply is turned on to bombard the copper-aluminum-silicon-chromium carbide quaternary composite carbide target. The composite functional layer is deposited by pure medium-frequency sputtering. The medium-frequency power supply frequency is 30 kHz, the power density is 8 W / cm², the tooling applies a negative bias voltage of -200 V, the argon flow rate is 40 sccm, the working pressure is 0.6 Pa, the deposition temperature is 300℃, and the deposition time is 90 minutes. A copper-aluminum-silicon-chromium carbide composite functional layer with a thickness of 5 μm is obtained. This layer is a pure carbide system without nitrogen doping. S5. Oxide Surface Deposition: Turn off the intermediate frequency power supply and the heating power supply of the copper-aluminum-silicon-chromium carbide composite target. Turn on the radio frequency magnetron sputtering power supply to bombard the silicon dioxide target. Deposit the oxide surface layer by pure radio frequency sputtering. The radio frequency power supply frequency is 13.56 MHz, the power is 1000 W, the radio frequency self-bias mode is used, there is no additional tooling bias, the argon flow rate is 20 sccm, the working pressure is 0.4 Pa, the deposition temperature is 250℃, and the deposition time is 12 minutes. A silicon dioxide surface layer with a thickness of 0.5 μm is obtained. No diamond or diamond-like coating is deposited. S6. Cooling and unloading: Turn off the RF power supply, turn off the silicon dioxide target heating power supply, stop the argon gas supply, maintain a vacuum state, turn off the tooling heater, and let the wok cool naturally to room temperature with the furnace for about 2 hours; after cooling to room temperature, fill the chamber with nitrogen to atmospheric pressure, open the chamber door, take out the wok, and obtain a cookware product with a three-layer gradient composite coating on the surface.

[0024] The cookware product prepared in this embodiment has a total composite film thickness of 5.8 μm. Performance tests were conducted on it, and the results are as follows: Film adhesion: Grade 0 in cross-cut adhesion test, with completely smooth edges of 100 1 mm × 1 mm squares and no peeling; Surface hardness: HV1900, standard deviation ±50 HV, high hardness and good uniformity; High temperature resistance: After dry burning at 500℃ for 30 minutes, the film layer showed no discoloration, blistering, cracking, or peeling, and the color and gloss remained basically the same as before dry burning; Long-lasting non-stick performance: After 100 egg frying tests, the non-stick performance decreased by only 2.5%, with 100% non-stick rate in the first 50 tests and no serious sticking throughout the process; Safety performance: After heating at 500℃ for 30 minutes, no harmful substances such as fluorides and heavy metals were detected, meeting food contact safety standards.

[0025] Example 2 A method for preparing a PVD composite coated cookware differs from Example 1 only in the film thickness parameters: the titanium transition layer deposition time is 15 minutes and the thickness is 0.5 μm; the copper-aluminum-silicon-chromium carbide composite functional layer deposition time is 120 minutes and the thickness is 5.5 μm; and the silica surface layer deposition time is 24 minutes and the thickness is 0.8 μm. The total thickness of the composite film is 6.8 μm, and the other preparation conditions, process parameters, and raw material ratios are exactly the same as in Example 1.

[0026] The performance test results of the cookware product prepared in this embodiment are as follows: Film adhesion: Grade 0 in cross-cut adhesion test, no peeling; Surface hardness: HV1950, slightly higher than that in Example 1; High temperature resistance: After dry burning at 500℃ for 30 minutes, the film layer showed no discoloration or peeling; Durable non-stick performance: After 100 egg frying tests, the non-stick performance decreased by ≤12%; Safety performance: No fluoride or heavy metal leaching, meeting food contact safety standards.

[0027] Example 3 A method for preparing a PVD composite coated cookware differs from Example 1 only in the film thickness parameters: the titanium transition layer deposition time is 2 minutes, and the thickness is 0.1 μm; the copper-aluminum-silicon-chromium carbide composite functional layer deposition time is 45 minutes, and the thickness is 4.5 μm; the silica surface layer deposition time is 7 minutes, and the thickness is 0.2 μm; the total thickness of the composite film is 4.8 μm. All other preparation conditions, process parameters, and raw material ratios are exactly the same as in Example 1.

[0028] The performance test results of the cookware product prepared in this embodiment are as follows: Film adhesion: Grade 1 in cross-cut adhesion test, with slight edge peeling of less than 5%, still meeting the requirements for actual use; Surface hardness: HV1800, slightly lower than that of Example 1; High temperature resistance: After dry burning at 500℃ for 30 minutes, the film layer showed slight discoloration, with no blistering, cracking, or peeling; Long-lasting non-stick performance: After 100 egg frying tests, the non-stick performance decreased by ≤15%, with no serious sticking; Safety performance: No fluoride or heavy metal leaching, meeting food contact safety standards.

[0029] Example Effect Analysis Based on Examples 1, 2, and 3, this invention employs a three-layer gradient structure consisting of a pure titanium transition layer, a copper-aluminum-silicon-chromium carbide composite functional layer, and a silica surface layer. Through a multi-power source independent deposition process involving pure multi-arc sputtering, pure mid-frequency sputtering, and pure radio-frequency sputtering, a PVD composite coating cookware system free of nitrogen carbides and oxides was successfully prepared, completely avoiding the existing technical routes of chromium-based paints and nitride / carbonitride coatings. Example 1 represents the optimal parameter scheme, achieving optimal film adhesion, high-temperature resistance, and long-lasting non-stick performance. Example 2 represents the upper limit parameter scheme, resulting in higher film hardness and stronger barrier properties, with overall performance close to that of Example 1. Example 3 represents the lower limit parameter scheme, with performance slightly lower than Example 1, but still meeting the basic requirements for long-lasting non-stick and high-temperature resistance in cookware. This demonstrates the good feasibility and adaptability of the technical parameter range of this invention.

[0030] The technical solution of this invention represents a significant breakthrough in cookware surface treatment technology. Compared with existing nitride-based PVD-coated cookware, it has significant advantages in high-temperature resistance, long-lasting non-stick performance, and high-temperature stability. Furthermore, the process is simplified, costs are reduced, and it is healthy and environmentally friendly, fully meeting the comprehensive performance requirements of modern cookware for long-lasting non-stick properties, high-temperature resistance, long lifespan, and health and environmental friendliness. It is suitable for Chinese high-temperature stir-frying cooking scenarios and has broad prospects for industrial application.

[0031] The above description is merely an embodiment of the technical content of the present invention. Any modifications or variations made by those skilled in the art using the present invention are within the scope of the patent claims of the present invention, and are not limited to those disclosed in the embodiments.

Claims

1. A method for preparing a PVD composite coated cookware, characterized in that... Includes the following steps: S1. Perform surface cleaning and activation treatment on the metal cookware substrate, wherein the metal cookware substrate is a metal substrate that has not undergone plasma spraying chromium layer treatment; S2. Place the cleaned cookware into the PVD coating equipment and evacuate to a vacuum level ≤5×10⁻⁶. - ³Pa, the PVD coating equipment is equipped with 2 pure titanium targets, 6 copper-aluminum-silicon-chromium carbide quaternary composite carbide targets and 2 oxide targets, and only argon gas is introduced as the working gas throughout the process. S3. Turn on the bias power supply to -800V to -1200V, use a pulse mode with a duty cycle of 20% and turn on the multi-arc power supply to generate argon ions and metal ions to bombard the surface of the cookware for plasma cleaning; after cleaning, reduce the bias voltage to -400V to -500V, adjust the duty cycle to 40%-50%, and continue to bombard the pure titanium target with the multi-arc power supply to deposit a pure titanium transition layer on the substrate surface. No chromium metal layer or chromium nitride layer is deposited. The titanium transition layer is not nitrided and has a thickness of 0.1–0.5μm. S4. Turn off the multi-arc bias and turn on the intermediate frequency power supply to bombard the copper-aluminum-silicon-chromium carbide quaternary composite carbide target to deposit a copper-aluminum-silicon-chromium carbide composite functional layer on the titanium transition layer. The composite functional layer is a pure carbide system and the thickness of the composite functional layer is 4.5–5.5 μm. S5. Turn on the RF power supply or pulsed DC power supply to bombard the oxide target and deposit an oxide surface layer on the surface of the composite functional layer. The thickness of the oxide surface layer is 0.2–0.8 μm. S6. After coating is completed, the furnace is cooled to room temperature.

2. The method for preparing cookware according to claim 1, characterized in that, In step S3, argon gas with a purity of 99.999% is introduced, and the surface of the cookware is plasma cleaned using a multi-arc high bias voltage. The cleaning parameters are: bias voltage -800 to -1200 V, argon gas flow rate 50–100 sccm, working pressure 0.5–1.0 Pa, and cleaning time 10–20 min. There is no combined deposition of cathode arc and sputtering process during the cleaning process.

3. The method for preparing cookware according to claim 1, characterized in that, In step S3, the titanium transition layer deposition parameters are: bias voltage -400 to -500 V, multi-arc current 60–100 A, argon flow rate 20–50 sccm, working pressure 0.3–0.8 Pa, deposition temperature 200–300℃, and the deposition process is pure multi-arc deposition without sputtering.

4. The method for preparing cookware according to claim 1, characterized in that, The copper-aluminum-silicon-chromium carbide quaternary composite carbide target is prepared by powder metallurgy sintering. In step S4, the intermediate frequency power supply has a frequency of 20–40 kHz, a power density of 5–10 W / cm², an argon flow rate of 30–60 sccm, a working pressure of 0.4–0.9 Pa, and a deposition temperature of 250–350 °C. The deposition process is pure intermediate frequency sputtering without the participation of cathode arc process.

5. The method for preparing cookware according to claim 1, characterized in that, In step S5, the oxide target is a silicon dioxide target, the radio frequency power supply frequency is 13.56 MHz, the power is 500–1500 W, the argon flow rate is 10–30 sccm, the working pressure is 0.2–0.6 Pa, the deposition temperature is 200–280℃, and the deposition process is pure radio frequency / pulse DC sputtering without the participation of cathode arc or multi-arc processes.

6. The method for preparing cookware according to claim 1, characterized in that, In step S1, the surface cleaning and activation treatment is a three-stage cleaning process: ultrasonic alkaline washing → acid washing and activation → deionized water rinsing → drying.

7. A PVD composite coated cookware, characterized in that, Prepared by the preparation method according to any one of claims 1 to 6, comprising: The metal cookware substrate is a metal substrate that has not undergone plasma spraying of a chromium layer or chromium-free base paint treatment; A pure titanium transition layer is deposited on the surface of the metal cookware substrate, forming a metallurgical bond with the substrate. It has a chromium-free / chromium nitride-free underlayer and a cathode arc + sputtering composite substrate structure. The thickness of the titanium transition layer is 0.1–0.5 μm. A copper-aluminum-silicon-chromium carbide composite functional layer is deposited on a titanium transition layer. This composite functional layer is a pure carbide system without nitrogen doping. It consists of 0.5–5% copper, 3–20% aluminum, 10–25% silicon, and 45–75% chromium carbide by weight. The thickness of the composite functional layer is 4.5–5.5 μm. The oxide surface layer, deposited on the surface of the composite functional layer, is a dense silica barrier layer without diamond or diamond-like coating. The thickness of the oxide surface layer is 0.2–0.8 μm.

8. The PVD composite coated cookware according to claim 7, characterized in that, The total thickness of the titanium transition layer, the copper-aluminum-silicon-chromium carbide composite functional layer, and the oxide surface layer is 3–6.8 μm.

9. The PVD composite coated cookware according to claim 7, characterized in that, The copper-aluminum-silicon-chromium carbide composite functional layer is composed of 1%-3% copper, 5%-15% aluminum, 15%-20% silicon, and 50%-70% chromium carbide by weight.

10. The PVD composite coated cookware according to claim 9, characterized in that, The total thickness of the titanium transition layer, the copper-aluminum-silicon-chromium carbide composite functional layer, and the oxide surface layer is 5–6 μm, and its high-temperature resistance reaches 500°C for 30 minutes of dry burning without discoloration or peeling.

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