Silicon-Doped Transition Metal Boride Coatings for Oxidation Resistance
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Solution Overview
Problem
Existing transition metal boride coatings exhibit poor oxidation resistance at high temperatures, particularly between 800° C. and 1500° C., limiting their application in high-performance components.
Innovation Solution
A coated article with a protective layer composed of transition metal borides and silicon as a dopant, formulated as TMxBySiq, where y/x ≥ 2, promotes the formation of a dense Si-enriched oxide scale, enhancing oxidation resistance by incorporating a separate crystalline Si phase and an oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If transition metal boride coatings are used to provide high temperature stability and refractory properties, then melting temperature and thermal conductivity are improved, but oxidation resistance deteriorates
Solution Approach 1:
The patent applies composite materials by combining transition metal borides (CrB2, HfB2) with silicon dopant to create a composite coating system. The silicon forms a separate crystalline Si phase that creates a protective oxide scale, while the transition metal boride matrix provides high temperature stability. This composite structure resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous microstructure with distinct phases: the transition metal boride matrix maintains high temperature stability, while the silicon-rich regions form protective oxide scales. The dopant concentration is optimized (0.1 ≤ q ≤ 0.40) to ensure sufficient silicon forms protective phases without compromising the overall coating structure.
2Stability of the object's composition
If transition metal boride coatings are used to provide strong thermo-shock resistance, then thermal shock resistance is improved, but oxidation resistance at elevated temperatures deteriorates
Solution Approach 1:
The composite coating system combines the thermo-shock resistance of transition metal borides with the oxidation protection of silicon-based oxide scales. The dual-phase structure allows the coating to maintain mechanical integrity under thermal cycling while forming protective oxidation barriers at the surface.
Solution Approach 2:
The patent changes the chemical composition parameters by introducing silicon dopant with controlled concentration (0.1 ≤ q ≤ 0.40). This compositional modification enables the formation of protective oxide phases without significantly altering the thermal expansion and mechanical properties of the underlying transition metal boride matrix.
3Reliability
If silicon is added as dopant to form Si-enriched oxide scale, then oxidation resistance is improved, but coating composition complexity increases
Solution Approach 1:
The patent uses parameter changes by precisely controlling the silicon dopant concentration within specific ranges (0.1 ≤ q ≤ 0.40). This quantitative approach optimizes oxidation protection while maintaining manageable coating complexity. The stoichiometric relationships (y/x ≥ 2, x+y+q=1) provide a systematic framework for composition design.
Solution Approach 2:
The silicon dopant creates local silicon-rich phases that form protective oxide scales, while the bulk coating maintains the simple transition metal boride structure. This localized modification approach improves oxidation resistance without requiring complex overall coating composition.
4Object-affected harmful factors
If water vapor is present in the environment, then volatile boric acid formation is expedited, but oxidation resistance deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming a protective oxide scale during coating fabrication or initial service exposure. This pre-established barrier prevents water vapor from reaching the transition metal boride substrate and initiating the harmful formation of volatile boric acid. The silicon-rich oxide scale acts as a proactive defense against environmental moisture.
Solution Approach 2:
The silicon-based oxide scale serves as an intermediary layer between the transition metal boride coating and the humid environment. This intermediate barrier prevents direct interaction between water vapor and the boride coating, blocking the chemical pathway that leads to boric acid formation and volatile boria.
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 coated article achieves oxidation kinetics of 10−9 to 10−13 kg²m⁻⁴s⁻¹ at 1100° C., significantly improving the oxidation resistance of transition metal borides at high temperatures.
Implementation Method 1
the protective layer promotes the formation of a dense Si-enriched oxide scale, enhancing oxidation resistance
Implementation Method 2
the coating system comprising a transition metal boride coating layer with capability to form an oxidation barrier coating layer
Data Source
AI summary
A coated article includes a coated surface which consists of a substrate and a coating system. The coating system has at least one protective layer consisting of one or more transition metal borides and one dopant element, wherein: 13 the protective layer having chemical element composition defined by the formula TMxBySiq, where TM is one or more of the transition metal elements Chromium and Hafnium; Si is Silicon present in the protective layer as the dopant element; B is Boron; x is the concentration in atomic percent of TM; y is the concentration in atomic percent of B; and q is the concentration in atomic percent of Si, where x+y+q=1, 0.15≤x≤0.33, 0.40≤y≤0.67, and 0.1≤q≤0.40, and—the atomic concentration ratio of boron to the transition metals in the protective layer is higher or equal to 2, i.e. y/x≥2, and—the protective layer exhibits an AlB2 crystal structure.