Thermal Spray Coating Resists Molten Metal Permeation
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Solution Overview
Problem
Thermal spray coatings used in molten metal baths are prone to damage due to permeation and dispersion of metal components, leading to reduced durability over time.
Innovation Solution
A thermal spray powder comprising tungsten, molybdenum, cobalt, nickel, iron, carbon, boron, and silicon, with specific mole ratios and crystal phases, is used to form a coating that minimizes metal component permeation, offering superior molten metal resistance and thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal spray coating is formed using conventional powder (tungsten carbide, tungsten boride, and cobalt particles), then the coating provides initial durability improvement, but metal components from the molten metal bath permeate and disperse into the coating over time, causing it to become prone to damage
Solution Approach 1:
The invention changes the chemical composition parameters of the thermal spray powder by introducing silicon as a key element (4-20 atomic %) and optimizing the ratios of tungsten, cobalt, and carbon. This compositional parameter change creates a coating with enhanced resistance to metal permeation while maintaining durability, directly resolving the contradiction between initial durability and long-term compositional stability
Solution Approach 2:
The invention creates a composite material system combining tungsten carbide, tungsten boride, cobalt, and silicon in specific proportions. This composite structure provides both the mechanical durability needed for molten metal bath environments and the chemical stability to resist metal permeation, as the silicon-containing phases act as barriers to metal diffusion while the carbide and boride phases provide structural integrity
2Duration of action of stationary object
If the coating is exposed to molten metal bath for prolonged periods, then the coating initially protects the roll, but metal components permeate and disperse into the coating, leading to gradual damage and reduced performance
Solution Approach 1:
Silicon acts as an intermediary element in the coating composition, forming silicon-containing phases that serve as a barrier between the molten metal bath and the underlying coating structure. This intermediary layer prevents direct interaction and permeation of metal components, thereby extending the roll's service life while maintaining coating reliability during prolonged exposure
Solution Approach 2:
The invention modifies the chemical composition parameters by incorporating silicon at optimized levels (4-20 atomic %) and adjusting the ratios of other elements. This parameter change enhances the coating's resistance to molten metal penetration, allowing the coating to maintain its protective function and reliability even after extended service in the molten metal bath
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 coating significantly enhances the durability and resistance to molten metals, preventing metal component permeation and maintaining performance even after prolonged use in molten metal baths.
Implementation Method 1
metal components in the molten metal bath permeate and disperse into the thermal spray coating
Implementation Method 2
The thermal spray powder has a crystal phase that contains cobalt, nickel, or iron; tungsten; and carbon or a crystal phase that contains cobalt, nickel, or iron; tungsten or molybdenum; and boron
Data Source
AI summary
A thermal spray powder is provided that contains, as constituent elements, a first element selected from W and Mo; a second element selected from Co, Ni, and Fe; a third element selected from C and B; and a fourth element formed of Si. The amount of the second element in the thermal spray powder is 40% by mole or less. The mole ratio of the fourth element to the second element in the thermal spray powder is 0.002 or greater and 0.03 or less. The thermal spray powder has a crystal phase containing Co, Ni, or Fe; W; and C or a crystal phase containing Co, Ni, or Fe; W or Mo; and B. In an X-ray diffraction spectrum of the thermal spray powder, the peak intensity attributed to Co, Ni, or Fe is at most 0.1 times the largest peak intensity in the same X-ray diffraction spectrum.