Technology： Other surface modification technologiesCDC-ZAC coating

CDC-ZAC coating process

Fine Ceramic Coating by Chemical Densified Process

CDC-ZAC coating consists of compound fine-ceramics with Cr₂O₃ as the principal component. The coating offers superior properties of nonporous, high hardness, high adhesive strength, and a low friction-coefficient. CDC-ZAC’s outstanding features are ideally suited to mechanical parts requiring anti-abrasion, anti-cavitation, and other attributes.

Major features

Nonporous

The formed film is a high-density coating composed of a chromium oxide-based composite fine ceramic with an average particle size of about 2 microns. The nonporousness prevents corrosive liquids or gases from penetrating to the substrate.

High hardness

CDC-ZAC consists of hard ceramic particles with HV1,600–2,000 and has an average cross-sectional hardness of HV1,000–1,200.

High adhesive strength

CDC-ZAC has high adhesive strength on the intermediate layer boundary, where Fe in the substrate and Cr in the coating diffuse mutually and combine chemically.

High density

CDC-ZAC has extremely strong adhesion among particles. Chromium oxide formed in the coating after a chemical densified process combines chemically with other compound-oxides constructing the base.

Representative properties of the coating

Wearing resistance

The high-hardness and high-density of CDC-ZAC provides superior wear resistance. The chrome oxide in the coating is comprised of particles with an average size of 2 microns, which improves lubrication effect and wearing resistance, while limiting heat generated at the sliding area.

Corrosion resistance

CDC-ZAC is resistant to many kinds of corrosives, such as seawater, base, and most types of acid and solvents, but does not provide sufficient resistance to hydrochloric acid, fluorine, or nitric acid. The table shows presents our in-lab measurements of the resistance. The extent to which CDC-ZAC can extend equipment life will depend largely on substrate material.

Reduction of deuterium permeation

(PDF: Reduction of Deuterium Permeation.pdf Provided by JAEA, Japanese-language only)

CDC-ZAC coating successfully reduced deuterium permeation to 1/1000 at 600℃ environment.

Scope of CDC-ZAC application

Coating thickness

It is possible to form coating thickness ranges from of 30–100 microns, with a standard thickness of 50 microns.

Substrate

CDC-ZAC coating is applicable to carbon steel, alloy steel, cast iron, titanium, inconel, sintered ceramic, and other materials. Aluminum surfaces must be prepared with an anodizing film coating.

Configuration and dimension of the object to be processed

Workpieces, including complicated objects, can be coated up to a maximum 400 mm external diameter and 2,000 mm length, and minimum 3 mm internal diameter.

CDC-ZAC process flow

ZACROM

Hard Cr plating has excellent hardness but poor corrosion resistance because of the many cracks on its surface that extend to substrate. ZACROM is a reinforced compound coating that fills the cracks with special ceramics.

Features

• High corrosion resistance even after exposure high temperatures of 300–400℃
• Cracks do not expand or spread after repeated stress effects
• Coating retains original Cr plating hardness

ZACROM coating achieves 5 to 50 times higher durability than Cr plating even in a corrosive environment.

Corrosion resistance

Refer to the photos below.

SUPER-ZAC

SUPER ZAC coating, a compound ceramic coating mainly containing SiO₂ and Cr₂O₃, is a newly-developed CDC-ZAC coating that further improves corrosion resistance.

Because of its excellent heat and wear resistance, SUPER-ZAC shows corrosion resistance superior to glass- and plastic-lining processes in high-temperature conditions.

In addition, its conformance to substrate expansion and contraction enables application to austenitic stainless steel with a high heat-expansion coefficient.

Wearing resistance

The chart shows the result of Ogoshi friction test. SUPER ZAC coating wear resistance outperforms SUS304 stainless steel and SS400 steel. SUPER ZAC provides consistent wear resistance under various conditions due to the low fluctuation of specific wearing loss at all friction rates.

Corrosion resistance

Refer to the photos below.