# US 12,006,586 B2 · Object comprising a chromium-based coating with a high Vickers hardness, production method, and aqueous electroplating bath therefor

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- Number: US 12,006,586 B2
- Document ID: US12006586B2
- Status: Granted
- Kind: B2
- Application number: 17/996,632
- Filed: 2021-04-21
- Published: 2023-04-27
- Granted: 2024-06-11
- Earliest claimed: 2020-04-23
- Assignees: Savroc Ltd
- Applicants: Savroc Ltd
- Inventors: Jussi Räisä; Arto Yli-Pentti
- Web page: https://patentgrep.com/patent/US12006586B2

## CPC

- C25D 3/06: from solutions of trivalent chromium
- C25D 3/10: characterised by the organic bath constituents used
- C25D 5/14: two or more layers being of nickel or chromium, e.g. duplex or triplex layers
- C25D 5/617: {Crystalline layers}
- C25D 5/50: by heat-treatment
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR

## Abstract

An object comprising a chromium-based coating on a substrate is disclosed, wherein the chromium is electroplated from an aqueous electroplating bath comprising trivalent chromium cations, wherein the chromium-based coating comprises 87-98 weight-% of chromium, 0.3-5 weight-% of carbon, and 0.1-11 weight-% of nickel and/or iron, and wherein the chromium-based coating has a Vickers microhardness value of 1000-2000 HV, and wherein the chromium-based coating does not contain chromium carbide. Further is disclosed a method for its production, and an aqueous electroplating bath.

## Claims

### Claim 1

An object comprising:
a chromium-based coating on a substrate, wherein chromium of the chromium-based coating is electroplated from an aqueous electroplating bath comprising trivalent chromium cations, wherein the chromium-based coating comprises 87-98 weight-% of chromium, 0.3-3 weight-% of carbon, and 0.1-11 weight-% of nickel and/or iron, and wherein the chromium-based coating has a Vickers microhardness value of 1000-2000 HV, and wherein the chromium-based coating does not contain chromium carbide.

### Claim 2 (depends on 1)

The object of claim 1, wherein the chromium-based coating has a Taber index of below 1.5 milligrams (mg)/1000 Rotations Per Minute (RPM), or below 1.3 mg/1000 RPM, or below 1.2 mg/1000 RPM, or below 1.1 mg/1000 RPM as determined according to ASTM G195-18, wherein the Taber index is calculated as ((A−B)/1000)/C, wherein A is the initial weight, B is the final weight, and C is the amount of RPM.

### Claim 3 (depends on 1)

The object of claim 1, wherein the crystal size of the chromium is 7-40 nanometers (nm), or 9-20 nm, or 11-16 nm.

### Claim 4 (depends on 1)

The object of claim 1, wherein the chromium-based coating has a Vickers microhardness value of 1000-1900 HV, or 1100-1800 HV, or 1200-1700 HV, or 1300-1600 HV, or 1400-1500 HV.

### Claim 5 (depends on 1)

The object of claim 1, wherein the object is a gas turbine, shock absorber, hydraulic cylinder, linked pin, joint pin, a bush ring, a round rod, a valve, a ball valve, or an engine valve.