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Method for producing a chromium coating on a metal substrate

A metal substrate and coating technology, applied in the direction of metal material coating process, coating, superimposed layer plating, etc. And corrosion resistance is not enough to meet industrial needs and other problems, to achieve the effect of excellent corrosion resistance, safety and toxicity

Active Publication Date: 2015-10-21
SAVROC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] The hardness, friction coefficient, wear resistance and corrosion resistance of known trivalent Cr coatings are insufficient to meet industrial needs
State-of-the-art coating processes cannot produce coatings with Vickers microhardness values ​​of approximately 2000 HV or greater

Method used

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  • Method for producing a chromium coating on a metal substrate
  • Method for producing a chromium coating on a metal substrate
  • Method for producing a chromium coating on a metal substrate

Examples

Experimental program
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Effect test

example 1

[0064] To demonstrate the effectiveness of the invention, several metal substrates were coated with nickel and chromium and subjected to a dual heat treatment sequence. The coated metal substrates used in the tests consisted of a steel substrate covered by a Ni-P layer with a thickness of 7 μm and a Cr layer with a thickness of 4 μm.

[0065] A first heating step is performed at a temperature between 200°C and 700°C for 30 or 45 minutes, after which the metal substrate is cooled. A second heating step of the same sample was performed at a temperature between 400° C. and 700° C. for a duration between 5 and 30 minutes, after which the metal substrate was cooled again.

[0066] The hardness values ​​of the coated and heat-treated metal substrates are measured in the microscopic range by Vickers hardness testing according to EN-ISO6507, depending on the thickness of the coating, using a durometer indenter weight of 5, 10 or 25 g.

[0067] The corrosion resistance of the coated a...

example 2

[0084] The steel substrate was coated with a Ni-P layer with a thickness of 7 μm and a Cr layer with a thickness of 4 μm. The heat treatment was performed in two steps: the first step took 45 minutes at 400°C and the second step took 30 minutes at 700°C.

[0085] The hardness value measured from the coating after the double heat treatment was about 2500 HV, measured with a load of 10 g.

[0086] The layered structure can be identified in cross-sectional micrographs of the coated surface. The composition of the coating is analyzed by energy dispersive X-ray spectroscopy (EDS) by having the electron beam lined up on the image and generating a scattergram of the relative proportions of the previously determined elements along the spatial gradient. image 3 The EDS spectrum of the sample is shown. On the left is the steel substrate. On the right is the outer surface of the coating.

[0087] Working from the steel substrate towards the outer surface of the coating, the followin...

example 3

[0096] Another steel substrate was coated with a similar coating as in example 2: nickel phosphorus layer with a thickness of 7 μm and a layer of chromium with a thickness of 4 μm. The heat treatment was performed in two steps: the first step took 30 minutes at 400°C and the second step took 30 minutes at 700°C.

[0097] Hardness values ​​measured from the coated and heat-treated metal substrates were approximately 2500-3000 HV, measured with a load of 10 g.

[0098] The lamellar structure can be identified in cross-sectional micrographs of the coating. Figure 5 EDS of samples are shown. Working from the steel substrate towards the outer surface of the coating, the following layers were able to be identified in the sample:

[0099] - Fe-rich layer (steel substrate),

[0100] - a layer mainly comprising Fe and Ni,

[0101] - a layer mainly comprising Ni and P,

[0102] - a layer mainly comprising Ni and Cr,

[0103] - a layer mainly comprising Cr and O,

[0104] - A lay...

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Abstract

In the method for producing a trivalent chromium based coating on a metal substrate,a layer of nickel phosphorus alloy is deposited on a metal substrateanda trivalent chromium layer is electroplated on the Ni-P layer. The coated metal substrate is subjected to one or more heat treatments to harden the coating and to produce multiphase layers including at least one layer containing crystalline Ni and crystalline Ni 3 P, and at least one layer containing crystalline Cr and crystal- line CrNi.By using this method it is possible to pro- duce coatings having a Vickers microhardness value higher than 2000 HV.

Description

technical field [0001] The present invention relates to a method for producing trivalent chromium-based coatings on metal substrates. The invention also relates to a coated article produced by said method. Background technique [0002] Chromium coatings are widely used as surface coatings for metal articles due to their high hardness values, attractive appearance, and excellent wear and corrosion resistance. Traditionally, Cr deposition is accomplished by electroplating from an electrolytic bath containing hexavalent Cr ions. The process is highly toxic in nature. Many efforts have been made to develop alternative coatings and coating processes to replace hexavalent Cr in electroplating. Among these alternative processes, trivalent Cr plating is attractive due to its low cost, ease of fabrication by using environmentally friendly and non-toxic chemicals, and ability to produce bright Cr deposits. However, there is still a lack of an industrial-scale process that imparts ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C25D3/06C23C28/02C25D5/50
CPCC23C28/345C23C12/00C23C12/02C23C18/1651C23C18/1694C23C18/1844C23C18/32C23C18/36C23C28/321C23C28/341C25D3/06C25D5/14C25D5/50Y10T428/12944C25D5/627C25D5/617C23C14/22C23C16/45525C25D5/505
Inventor J·米耶蒂宁J·雷伊赛
Owner SAVROC
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