Method for Producing Chromium-Containing Multilayer Coating and a Coated Object

• US 20160333493A1
• Filed: 01/15/2014
• Published: 11/17/2016
• Est. Priority Date: 01/15/2014
• Status: Active Grant

• Current Assignee: Savroc Ltd.
• Original Assignee: Savroc Ltd.
• Inventors: Miettinen, Juha, Ris, Jussi
• Granted Patent: US 10,443,142 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C23C 14/24 Vacuum evaporation
• CPC Class Codes: C23C 16/44 characterised by the method of coating C23C16/04 takes precedence
• CPC Class Codes: C23C 16/45525 Atomic layer deposition [ALD]
• CPC Class Codes: C23C 18/1653 Two or more layers with at least one layer obtained by electroless plating and one layer obtained by electroplating
• CPC Class Codes: C23C 18/1692 Heat-treatment
• CPC Class Codes: C23C 18/32 Coating with nickel, cobalt or mixtures thereof with phosphorus or boron C23C18/50 takes precedence
• CPC Class Codes: C23C 28/02 only coatings only including layers of metallic material
• CPC Class Codes: C23C 28/021 including at least one metal alloy layer
• CPC Class Codes: C23C 28/023 only coatings of metal elements only
• CPC Class Codes: C23C 28/42 characterized by the composition of the alternating layers
• CPC Class Codes: C25D 3/06 from solutions of trivalent chromium
• CPC Class Codes: C25D 3/562 containing more than 50% by weight of iron or nickel or cobalt
• CPC Class Codes: C25D 5/14 two or more layers being of nickel or chromium, e.g. duplex or triplex layers
• CPC Class Codes: C25D 5/50 by heat-treatment
• CPC Class Codes: C25D 5/625 Discontinuous layers, e.g. microcracked layers
• CPC Class Codes: C25D 5/627 Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance

Abstract

To produce a chromium-containing multilayer coating on an object, alternate layers of nickel phosphorus alloy and trivalent chromium are deposited on the object until a desired thickness of coating has been reached. The coated object is then subjected to one or more heat treatments to improve the mechanical and physical properties of the coating and to produce multiphase layers comprising layers containing crystalline Ni and crystalline Ni₃P and layers containing crystalline Cr.

Claims

1. A method for producing a chromium-containing multilayer coating on an object, comprising the steps of:

depositing a layer of nickel-phosphorus alloy (NiP) on the object;

electroplating a layer of trivalent chromium on the object;

repeating said steps one or more times in order to produce a multilayer coating containing two or more alternate layers of nickel-phosphorus alloy and chromium; and

subjecting the coated object to one or more heat treatments to amend the mechanical and physical properties of the coating and to produce multiphase layers containing crystalline Ni and crystalline Ni₃P and multiphase layers containing crystalline Cr.

2. A method according to claim 1, wherein at least one of the chromium layers is deposited next to a NiP layer and during the heat treatment at least one multiphase layer is produced that contains crystalline CrNi.

3. A method according to claim 1, wherein at least one intermediate layer is deposited on the object between the layers of NiP and Cr, the intermediate layer consisting of a metal or metal alloy other than NiP or Cr.

4. A method according to claim 3, wherein the intermediate layer consists of nickel, copper or molybdenum, or an alloy containing any of them.

5. A method according to claim 4, wherein a strike layer is deposited between the chromium layer and the NiP layer.

6. A method according to claim 5, wherein the strike layer consists of sulphamate nickel, bright nickel, titanium, or any other suitable material.

7. A method according to claim 1, wherein the NiP layers are produced by electrodeposition or electroless deposition.

8. A method according to claim 1, wherein the phosphorus content of the nickel phosphorus alloy is 1-15 w-%, preferably 3-12 w-%, more preferably 5-9 w-%.

9. A method according to claim 1, wherein the temperature in the heat treatments is 200-1000°

C., preferably 400-750°

C., more preferably 500-700°

C.

10. A method according to claim 1, wherein at least two heat treatments are carried out after the desired number of coating layers has been deposited on the object.

11. A method according to claim 1, wherein at least one of the heat treatments is carried out at a temperature between 500 and 700°

C.

12. A method according to claim 1, wherein the object to be coated is of metal and the hardening of the metal of the object is carried out at the same time as the coated object is heat-treated.

13. A method according to claim 12, wherein the object to be coated is of steel and the heat treatment is carried out at a temperature between 750 and 1000°

C.

14. A method according to claim 1, further comprising the step of depositing a top layer on the coated and heat-treated object by thin film deposition, such as physical vapor deposition, chemical vapor deposition or atomic layer deposition.

15. A method according to claim 1, further comprising the step of depositing a top layer on the coated object by thin film deposition, such as physical vapor deposition, chemical vapor deposition or atomic layer deposition, before the step of subjecting the coated object to one or more heat treatments.

16. A coated object comprising a chromium-containing multilayer coating produced by a method according to claim 1, the coating comprising multiphase layers containing crystalline Ni and crystalline Ni₃P and multiphase layers containing crystalline Cr.

17. A coated object according to claim 16, further comprising at least one multiphase layer containing crystalline CrNi.

18. A coated object according to claim 16, further comprising at least one intermediate layer consisting of a metal or metal alloy other than NiP or Cr.

19. A coated object according to claim 18, wherein the intermediate layer consists of nickel, copper, or molybdenum, or an alloy containing any of them.

20. A coated object according to claim 16, further comprising a top layer produced by thin film deposition, such as physical vapor deposition or chemical vapor deposition.