CN100453700C - Surface gradient protective coating and its preparing method - Google Patents

Abstract

The invention relates to surface gradient protecting coat and manufacturing method. It uses protecting coat system design to adjust MoB and CoCr basis component content proportion without changing its essential component, make damping transition thermal spray coating material, and gain gradient thermal spray coating. The gradient protecting coat of the invention can obviously increase coating anti thermal shock property, and corrosion-resisting properties. Thus it can be used as surface protecting coat for the immerged and stable rollers used in continuous dip coating high aluminum zinc production line.

Description

A kind of surface gradient protective coating and preparation method thereof

Technical field

The present invention relates to a kind of surface gradient protective coating and preparation method thereof; specifically be surface graded protection hot spray coating of a kind of MoB/CoCr and manufacture method thereof, can be used for the coating for surface protection of (but being not limited to) continuously dip coat high aluminum zinc production line with sinking roller and stable roller.

Background technology

Hot dip high aluminum zinc (containing 55%Al) coated steel sheet is as the steel products of high added value, the low aluminium spelter coating steel plate of specific heat pure zinc plating and hot dip has better mechanical property, stronger oxidation-resistance, and have good coating, processibility and economy, particularly have excellent corrosion resistance nature; Be widely used in fields such as construction industry, household electrical appliance industry, industrial instrument industry and automotive industry, market outlook are boundless.

Yet sinking roller and stable roller use working conditions quite abominable as the most critical component in the core work package on the whole piece galvanization production line, are very easy to produce surface failure and surface imperfection.And the variation of sinking roller and stable roll surface surface quality not only can have a strong impact on the quality of high aluminum zinc coated steel sheet, the grade of reduction product, more can have a strong impact on the high continuity rhythm of hot dip high aluminum zinc production line steady operation, significantly reduces production efficiency.Simultaneously, hot pure zinc plating commonly used and low aluminium zinc can't satisfy the long lifetime service requirements of current actual production with sinking roller and stable roller WC/CoCr coating.Therefore, sinking roller and stable roller are short work-ing life, just become restriction hot dip high aluminum zinc plate hight and imitate the bottleneck factor of producing.

At present, prolong in multiple employing coating for surface protection method in the middle of the approach in hot dip high aluminum zinc sinking roller and stable roller work-ing life, it is very effective going back none.Handle as using, contain W, Co etc. and be difficult for precious metal element iron-based corrosion and heat resistant alloy with aluminium zinc fusant reaction, can partly prolong the work-ing life of sinking roller and stable roller through sealing of hole.But, since the iron-based component can with the molten aluminum generation kickback in the molten metal, and early failure coating; And make coating to reuse, thereby improve Financial cost.And use aluminum-spinel ceramic surface coating, can significantly improve the surperficial erosion resistance of sinking roller and stable roller.But, because aluminum-spinel pottery (Al ₂O ₃-MgO system) relatively poor with the matching that sinks between roller and the stable roller metal mother metal, particularly thermal expansivity (20-650 ℃ of aluminum-spinel thermal expansivity is 7.8 * 10 ^-6K, sinking roller and stable roller metal mother metal thermal expansivity are 18.9 * 10 ^-6/ K), furthermore the ceramic phase material fragility is big, and coating is very easy to stress crack take place or peel off, and is difficult to satisfy the long lifetime service requirements of roller.Similarly, for novel MoB/CoCr metal-ceramic compound coating, its thermal expansivity is usually in (9.0-11.6) * 10 ^-6/ K (temperature 100-700 ℃) scope, although itself and roller mother metal bonding strength height, erosion resistance is good; But the greatest differences on the thermospray coefficient between the two still makes coating for surface protection that stress crack takes place easily or peels off.

Usually, solve because of hot expansibility difference causes coating stress be full of cracks and the problem of peeling off, main adopt add the spray thermal expansivity between and supercoat and mother metal between the method for transition buffer layer.But under actual service condition, the spray material that selection and supercoat and mother metal all have matched well such as bonding strength is good, thermal expansion coefficient difference is little is very difficult, and this situation for pure ceramic phase material (as aluminum-spinel) more so.And if adopt when adding the middle transition buffer coating of spray more than three layers, its technology is very complicated again, the production cycle long, difficult quality is controlled, the Financial cost height, is unfavorable for practical application.Therefore, for sinking roller and stable roller coating for surface protection, go back the very effective solution route of none for the hot dip high aluminum zinc up to now.

Summary of the invention

The present invention is directed to above shortcomings and defective in the prior art; the system design thought of a kind of hot dip high aluminum zinc with sinking roller and stable roller MoB/CoCr gradient surface supercoat not only is provided, but also a kind of manufacture method of MoB/CoCr gradient surface supercoat is provided.Purpose is to make between MoB/CoCr coating for surface protection and the roller mother metal to have good matching, and then can satisfy the long-lived stable actual production service requirements of coating for surface protection.

Thought of the present invention mainly stems from the basis of applying in a flexible way to original position and these two notions of gradient: be different from pure ceramic phase aluminum-spinel coated material, the MoB/CoCr coated material mainly contains MoB base and two kinds of components of CoCr base, and has bigger hot expansibility difference (100-700 ℃ of MoB thermal expansivity about 8.0 * 10 between MoB base component and the CoCr base component ^-6/ K, CoCr thermal expansivity about 15.0 * 10 ^-6/ K), approaching sink roller and stable roller mother metal of the thermal expansivity of CoCr base component, and CoCr base component simultaneously and roller material can be realized good binding, content and ratio between two kinds of basal components of what is more important are adjustable.Therefore, adjust the ratio of the base of MoB in the coated material and CoCr base two components in situ, make it low near the roller material CoCr of place base component concentration height, MoB base component concentration; In that then MoB base component concentration height, CoCr base component concentration are low near the coating for surface protection place.That is: under the situation that does not change original coated material basal component, two kinds of component ratio content of the adjustment of gradient gradual change type; And then acquisition combines the surface gradient protective coating of good, anti-stress crack and strong, the anti-high aluminum zinc melt of peel-ability corrodibility excellence with roller mother metal coupling.This is the key point that the present invention significantly is different from other top coats.For achieving the above object, the present invention carries out following gradient cladding system design and gradient cladding preparation: 1, and the buffer transition layer between roller material and the coating for surface protection is 1 layer or 2 layers.As more than 3 layers, then can make the technology of actual production complicated, increase the Financial cost of product.2, the total thickness of sinking roller and the surface graded coating of stable roller is between 0.07-0.26mm; The thickness of buffer transition layer then should not be less than 1/6 of Bulk coat total thickness, if the thickness of buffer transition layer less than 1/6 of Bulk coat total thickness, then degree of its buffering transition is not ideal enough.3, should try one's best into the distribution of uniform gradient between buffer transition layer material coefficient of thermal expansion coefficient and roller material and the coating for surface protection thermal expansivity.When adopting 1 layer of buffer transition layer, the preferred (N of the numerical value of buffer transition layer material thermal expansion coefficient ₀± 1.3) * 10 ^-6/ K, $N_0=\frac{1}{2}(N_{\mathrm{BASE}}+N_{\mathrm{MoB}/\mathrm{CoCr}});$ Wherein, N _BASEBe roller material thermal expansivity, N _MoB/CoCrBe surface protection work coating thermal expansivity.When adopting 2 layers of buffer transition layer, near the preferred (N of the numerical value of roller material buffer transition layer material thermal expansion coefficient ₁± 0.6) * 10 ^-6The K scope, $N_1=\frac{2}{3}{N}_{\mathrm{MoB}/\mathrm{CoCr}}+\frac{1}{3}{N}_{\mathrm{BASE}};$ And the numerical value of the buffer transition layer material thermal expansion coefficient of close surface protection work coating, preferred (N ₂± 0.6) * 10 ^-6/ K scope, $N_2=\frac{1}{3}{N}_{\mathrm{MoB}/\mathrm{CoCr}}+\frac{2}{3}{N}_{\mathrm{BASE}}.$ 4, among the present invention, MoB base and CoCr basal component ratio in the buffering tie coat material can be carried out proximate calculation according to following composite design principle.M=[8.0V+15.0 (1-V)] * 10 ^-6/ K, wherein: the Coefficient of Thermal Expansion value that M sets for the buffer transition layer material, V is the volume content of MoB base component in the buffer transition layer material.Then (1-V) is the volume content of CoCr base component in the buffer transition layer material.5, the thermospray buffer transition layer material particle size with suitable ingredients ratio should be at the 10-70 mu m range.Producing of thermospray buffer transition layer powder can be adopted following dual mode: 1) prepare with raw material powder by the granulation sintering process.Raw material powder by set the percentage composition ratio, average particulate diameter is that the equal particle diameter of MoB powder peace of 4.5 μ m is that the CoCr alloy powder of 7 μ m is formed; After fully mixing powder and sintering, adopt aeroponics powder process, and sorting is to 10-70 μ m size range.The buffer transition layer powder characteristic that this mode makes is good, two kinds of phase component distributional stabilities and evenly, but cost is slightly high.2) prepare by mechanical mixing.Raw material powder by set the percentage composition ratio, average particulate diameter is that the equal particle diameter of MoB powder peace of 10-70 μ m is that the CoCr alloy powder of 10-70 μ m is formed, get final product through thorough mixing.Wherein, MoB powder and CoCr alloy powder granularity distribution range should be consistent as far as possible.This to produce mode simple and convenient, and cost is lower; But the distributing homogeneity of two kinds of phase components is slightly poor in the prepared buffer transition layer powder.6, among the present invention, supersonic flame spraying method is all adopted in the preparation of buffer transition layer and coating for surface protection.In coating forming procedure, use the Praxair/TAFA JP-5000 of company thermal spraying apparatus, processing parameter is as follows: oxygen gas flow rate be the 890-895 liter/minute, the kerosene flow velocity be the 0.3-0.35 liter/minute, spray distance is 350-390mm, and thermospray is the 45-53 gram/minute for powder speed.

Compared with prior art; the present invention has following beneficial effect: have good matching between sinking roller and stable roller coating for surface protection and the roller material; thereby significantly improved the anti-stress crack and the peel-ability of coating for surface protection, and then had the good melt of anti-high aluminum zinc corrosive nature.

Embodiment:

Specimen size Φ 70mm * 300mm, material is hot dip high aluminum zinc sinking roller/stablize roller steel 316L.Because MoB/CoCr surface protection work coating thermal expansivity is more little, then coating and roller material matching are poor more, and coating also just is easy to generate be full of cracks more and peels off; For this reason, present case is selected thermal expansivity N _MoB/CoCr=9.0 * 10 ^-6The MoB/CoCr sintering metal of/K is as surface protection work coated material.When adopting 1 layer of buffer transition layer, $N_0=\frac{1}{2}(N_{316L}+N_{\mathrm{MoB}/\mathrm{CoCr}})\≈14.0\×{10}^{-6}/K;$ When adopting 2 layers of buffer transition layer, $N_1=\frac{2}{3}{N}_{\mathrm{MoB}/\mathrm{CoCr}}+\frac{1}{3}{N}_{316L}\≈12.3\×{10}^{-6}/K,$ $N_2=\frac{1}{3}{N}_{\mathrm{MoB}/\mathrm{CoCr}}+\frac{2}{3}{N}_{316L}\≈15.6\×{10}^{-6}/K.$ Further, MoB base and CoCr basal component ratio in the buffering tie coat material can be carried out proximate calculation according to the composite design principle.The surface gradient protective coating design system of sinking roller and stable roller sees table 1 for details.MoB base and CoCr base component ratio calculate and get by above-mentioned composite design principle in the hot spraying powder, and produce by mechanical mixing, and powder granularity is at the 15-65 mu m range.

Supersonic flame spraying method is all adopted in the preparation of buffer transition layer and coating for surface protection.In coating forming procedure, use the Praxair/TAFA JP-5000 of company thermal spraying apparatus, processing parameter is as follows: oxygen gas flow rate be the 890-895 liter/minute, the kerosene flow velocity be the 0.3-0.35 liter/minute, spray distance is 350-390mm, and thermospray is the 45-53 gram/minute for powder speed.

Sample after the thermospray is used for thermal shock test.In thermal shock test, sample is heated to 670 ℃ of temperature and makes it whole soaking, then take out hardening and be cooled to room temperature; Repeat this program, crackle, peeling occur or peel off until the surface heat spray-on coating.If the number of times that the top coat thermal shock damages less than 5 times, is estimated with symbol * represent; If number of times between 5-10 time, is estimated and is represented with symbol zero; If number of times at 10-15 time, is estimated and is used symbol

Represent.Case study on implementation is all listed in the table 1 with the evaluation result that compares case.Wherein, the opposing of high thermal shock number of times explanation coating for surface protection cause stress crack because of not matching or the ability of peeling off strong, hang down the thermal shock number of times and reflect that then coating for surface protection is easy to generate the stress crack or peel off of not matching.As can be seen from the table, with the comparative example contrast, the supercoat of each embodiment all has good hot matching with the roller material.

Table 1 surface gradient protective coating embodiment and comparative example

Claims (5)

1, a kind of surface gradient protective coating; supercoat covers on the matrix; supercoat is made up of buffer transition layer and MoB/CoCr metal-ceramic compound coating; it is characterized in that; buffer transition layer is 1 layer or 2 layers, and the MoB base of buffer transition layer and two kinds of components contents ratios of CoCr base are determined by following formula: M=[8.0V+15.0 (1-V)] * 10 ^-6/ K, wherein: the Coefficient of Thermal Expansion value that M sets for the buffer transition layer material, V is the volume content of MoB base component in the buffer transition layer material, and then (1-V) is the volume content of CoCr base component in the buffer transition layer material;

When adopting 1 layer of buffer transition layer, the numerical value of buffer transition layer material thermal expansion coefficient M is (N ₀± 1.3) * 10 ^-6/ K, $N_0=\frac{1}{2}(N_{\mathrm{base}}+N_{\mathrm{MoB}/\mathrm{CoCr}});$

When adopting 2 layers of buffer transition layer, the numerical value of close roller material buffer transition layer material thermal expansion coefficient M is (N ₁± 0.6) * 10 ^-6/ K scope, $N_1=\frac{2}{3}{N}_{\mathrm{MoB}/\mathrm{CoCr}}+\frac{1}{3}{N}_{\mathrm{base}};$ And the numerical value of the buffer transition layer material thermal expansion coefficient M of close surface protection work coating is (N ₂± 0.6) * 10 ^-6/ K, $N_2=\frac{1}{3}{N}_{\mathrm{MoB}/\mathrm{CoCr}}+\frac{2}{3}{N}_{\mathrm{base}};$

Wherein, N _BaseBe roller material thermal expansivity, N _MoB/CoCrBe surface protection work coating thermal expansivity.

According to the described surface gradient protective coating of claim 1, it is characterized in that 2, the total thickness of surface gradient protective coating is between 0.07-0.26mm, the thickness of buffer transition layer then is not less than 1/6 of Bulk coat total thickness.

According to the described surface gradient protective coating of claim 1, it is characterized in that 3, thermospray buffer transition layer material particle size is at 10-70 μ m.

4; the preparation method of the described surface gradient protective coating of claim 1; it is characterized in that; supercoat covers on the matrix; supercoat is made up of buffer transition layer and MoB/CoCr metal-ceramic compound coating; the buffer transition layer raw material adopts the preparation of granulation sintering process; raw material powder is that the equal particle diameter of MoB powder peace of 4.5 μ m is that the CoCr alloy powder of 7 μ m is formed by average particulate diameter; MoB powder and CoCr alloy powder fully mix sintering behind the powder by claim 1 prescribed volume content; adopt aeroponics powder process and sorting; supersonic flame spraying method is all adopted in the preparation of buffer transition layer and coating for surface protection; in coating forming procedure; oxygen gas flow rate be the 890-895 liter/minute; the kerosene flow velocity be the 0.3-0.35 liter/minute, spray distance is 350-390mm, thermospray is the 45-53 gram/minute for powder speed.

5; the preparation method of the described surface gradient protective coating of claim 1; it is characterized in that; supercoat covers on the matrix; supercoat is made up of buffer transition layer and MoB/CoCr metal-ceramic compound coating; the buffer transition layer raw material adopts the mechanical mixing preparation; raw material powder is that the equal particle diameter of MoB powder peace of 10-70 μ m is that the CoCr alloy powder of 10-70 μ m is formed by average particulate diameter; MoB powder and CoCr alloy powder get final product through thorough mixing by claim 1 prescribed volume content; supersonic flame spraying method is all adopted in the preparation of buffer transition layer and coating for surface protection; in coating forming procedure; oxygen gas flow rate be the 890-895 liter/minute; the kerosene flow velocity be the 0.3-0.35 liter/minute; spray distance is 350-390mm, and thermospray is the 45-53 gram/minute for powder speed.