Laser Powder Bed Fusion Refractory Alloy Coating Crack Prevention
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Solution Overview
Problem
Refractory alloy coatings, such as CoMoCrSi, tend to crack and experience diffusion issues when applied using conventional methods like laser cladding, leading to reduced oxidation resistance and altered microstructures due to thermal mismatch and preheating processes.
Innovation Solution
The method involves using laser powder bed fusion (L-PBF) combined with a laser remelting process to deposit crack-free refractory alloy coatings on substrates without preheating, controlling scan speed and laser power to maintain chemical composition and prevent dilution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preheating the substrate is used to prevent cracking in laser cladding, then crack formation is reduced, but dilution between substrate and coating material increases, altering microstructure and material properties
Solution Approach 1:
The patent changes the laser processing parameters by using a lower laser power density and adjusted scan speed to deposit the coating without requiring substrate preheating. This parameter optimization allows the coating to be deposited at temperatures that prevent thermal mismatch cracking while avoiding excessive heat input that would cause substrate-coating dilution and microstructural alteration.
Solution Approach 2:
The patent extracts and eliminates the preheating step from the conventional laser cladding process. By removing this intermediate heating stage, the method avoids the associated dilution problem while still achieving crack-free coatings through optimized deposition parameters and controlled cooling rates during the actual coating formation.
2Strength
If conventional laser cladding is used to deposit refractory alloy coatings, then metallurgical bonding is achieved, but thermal stresses from temperature gradients induce crack formation
Solution Approach 1:
The patent optimizes laser power density and scan speed parameters to achieve a balanced thermal field that promotes strong metallurgical bonding while minimizing temperature gradients. The lower power density with adjusted scan speed creates a more uniform heat distribution that reduces thermal stresses during cooling, preventing crack formation while maintaining coating adhesion.
Solution Approach 2:
The patent employs periodic scanning patterns and controlled deposition rates to manage thermal accumulation. By controlling the heating cycle during deposition and allowing controlled cooling between passes, the method reduces peak thermal stresses that would otherwise cause cracking while maintaining sufficient heat input for strong bonding.
3Productivity
If thermal deposition techniques like HVOF are used to apply coatings, then deposition speed is high, but oxide content and porosity increase, reducing oxidation resistance
Solution Approach 1:
The patent replaces thermal field-based deposition (HVOF, APS) with a laser-based process that uses a more controlled energy input mechanism. The laser powder bed fusion approach allows precise control of melting and deposition, enabling high deposition rates while maintaining lower oxide content and porosity levels that compromise oxidation resistance.
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
This approach results in crack-free, high-hardness refractory alloy coatings with preserved properties, suitable for high-temperature applications, and is more scalable and efficient than conventional methods.
Implementation Method 1
forming a refractory alloy coating on a substrate using a laser powder bed fusion (L-PBF) process
Implementation Method 2
forming a refractory alloy coating on a substrate using a laser powder bed fusion (L-PBF) process
Implementation Method 3
removing cracks from the refractory alloy coating by remelting the refractory alloy coating with a laser
Implementation Method 4
removing cracks from the refractory alloy coating by remelting the refractory alloy coating with a laser
Data Source
AI summary
Methods of additive manufacturing of refractory alloy coating. Such methods include forming a refractory alloy coating on a substrate using a laser powder bed fusion (L-PBF) process with a refractory alloy and removing cracks from the refractory alloy coating by remelting the refractory alloy coating with a laser.