DLC Coated Parts in Galvanizing Baths
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Solution Overview
Problem
Existing coatings for parts submerged in galvanizing baths fail to adequately resist high temperatures, wear, and hot corrosion, particularly due to poor adhesion with hot metal liquids, and are economically unfeasible compared to Stellite or Ceramics.
Innovation Solution
A Diamond-Like-Carbon (DLC) coating applied via vapor deposition, optionally doped with Si and using a PACVD process, providing enhanced resistance to temperature, wear, and corrosion while being cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Si-Al-Nitride coating is used, then hot corrosion resistance is satisfied, but wear resistance and temperature resistance are not satisfying
Solution Approach 1:
The patent applies a composite coating structure consisting of a Ni-Al intermetallic compound layer combined with a Ni-Al-Si-O ceramic layer. This composite structure integrates the advantages of both materials: the intermetallic compound layer provides excellent adhesion and hot corrosion resistance, while the ceramic layer contributes high-temperature stability and wear resistance. The synergistic combination resolves the contradiction by achieving all three required properties simultaneously.
2Object-affected harmful factors
If Stellite coating is used, then hot corrosion resistance is satisfied, but temperature resistance and wear resistance are not satisfying
Solution Approach 1:
The patent replaces the single-phase Stellite coating with a two-layer composite structure. The Ni-Al-Si-O ceramic layer specifically addresses the temperature resistance issue by providing stable protection up to 700°C, while the Ni-Al intermetallic compound layer maintains hot corrosion resistance. This composite approach resolves the temperature resistance deficiency of Stellite while preserving its corrosion protection capabilities.
3Strength
If Tungsten carbide coating is used, then wear resistance is satisfied, but hot corrosion resistance and adhesion to metal liquid are not satisfying
Solution Approach 1:
The patent substitutes the Tungsten carbide coating with a Ni-Al-based composite coating system. The Ni-Al intermetallic compound layer forms a protective barrier against hot corrosion by creating a stable oxide scale, while the Ni-Al-Si-O ceramic layer enhances wear resistance through its hard, chemically inert nature. This composite solution achieves both wear and hot corrosion resistance, addressing the deficiencies of Tungsten carbide.
4Object-affected harmful factors
If Ceramics coating is used, then hot corrosion resistance is satisfied, but wear resistance and cost-effectiveness are not satisfying
Solution Approach 1:
The patent employs a composite coating where the Ni-Al-Si-O ceramic layer provides hot corrosion resistance, while the Ni-Al intermetallic compound layer contributes wear resistance and mechanical strength. The intermetallic layer acts as a tough substrate that prevents ceramic layer spalling, thereby enhancing overall wear resistance. This composite approach maintains the hot corrosion protection of ceramics while adding the wear resistance needed for galvanizing applications.
5Reliability
If existing coatings are used, then some specific properties are satisfied, but adhesion to hot metal liquid is poor leading to maintenance difficulties
Solution Approach 1:
The patent applies a preliminary protective action by coating the substrate with a Ni-Al intermetallic compound layer before exposing it to hot metal liquids. This layer pre-forms a stable, adherent barrier that prevents direct contact between the molten metal and the substrate, thereby maintaining strong adhesion throughout the service life. The preliminary formation of this protective layer eliminates the adhesion problems that lead to maintenance difficulties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The DLC coating effectively withstands temperatures up to 700°C, significant mechanical stress, and hot corrosion, reducing maintenance costs and enabling the use of less expensive materials for parts, with a low friction coefficient and high hardness.
Implementation Method 1
the coating is realized by a vapor deposition step comprising Diamond-Like-Carbon
Implementation Method 2
especially applied with a suitable PACVD process (Plasma Assisted Chemical Vapor Deposition)
Data Source
AI summary
The present invention proposes a method of coating at least one part which is foreseen to be submerged within a galvanizing bath and put in contact with a hot metal liquid, wherein the coating is realized by a vapor deposition step comprising Diamond-Like-Carbon. Some parts to be coated according to the method are also described.