Wear Part Hard Facing via Intermediate Layer Bonding
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Solution Overview
Problem
Existing methods for creating wear-resistant coatings on steel parts, such as welding and thermal spraying, often require high temperatures that can degrade the substrate and are economically inefficient, especially for large or complexly shaped parts, and result in inhomogeneous structures and cracking.
Innovation Solution
A wear part with a body of iron-group metal or alloy coated with a wear-resistant layer comprising metal carbides and a metal-based phase with a low liquidus temperature, bonded through an intermediate layer that includes silicon and chromium, allowing for a metallurgical bond at lower temperatures and preventing distortion of the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding or thermal spraying methods are used to apply hard facing, then wear resistance is improved, but substrate degradation and distortion occur due to high temperatures
Solution Approach 1:
The invention changes the temperature parameter by using a binder alloy with liquidus temperature below 1200°C, significantly lower than conventional hard facing methods. This allows the hard facing to be applied at temperatures that do not degrade the steel substrate or cause distortion, while still achieving metallurgical bonding and excellent wear resistance
Solution Approach 2:
The invention introduces an intermediate layer between the steel substrate and the hard facing layer. This intermediate layer acts as a thermal buffer, protecting the substrate from direct exposure to high temperatures during application while still enabling metallurgical bonding. The intermediate layer comprises the same binder alloy as the hard facing, creating a graded transition zone
2Reliability
If conventional hard facing methods are used, then wear resistance is achieved, but inhomogeneous structure and cracking occur
Solution Approach 1:
By controlling the temperature parameter to remain below the liquidus temperature of the binder alloy during service, the invention prevents excessive grain growth and phase transformations that lead to inhomogeneous structures. The low-temperature binder system maintains a fine, homogeneous microstructure throughout the hard facing layer, eliminating cracking issues
Solution Approach 2:
The invention creates a composite structure with multiple layers: steel substrate, intermediate layer, and hard facing layer. Each layer has optimized composition and properties, with the binder alloy serving as the matrix that binds carbide particles. This composite approach ensures homogeneous structure throughout while achieving superior wear resistance
3Manufacturing precision
If high sintering temperatures are used to achieve full density, then coating density is improved, but substrate distortion and melting occur
Solution Approach 1:
The invention fundamentally changes the temperature parameter by using a binder alloy with liquidus temperature below 1200°C. This allows achieving full density at temperatures below 1200°C through controlled sintering, eliminating substrate distortion and melting while maintaining coating integrity and density
Solution Approach 2:
The intermediate layer serves as a thermal mediator between the hard facing and steel substrate. During sintering, it protects the substrate from direct high-temperature exposure while allowing the hard facing to achieve full density through controlled diffusion and bonding processes at lower temperatures
4Reliability
If diamond grains are incorporated into hard facing, then ultra-hard properties are achieved, but diamond degradation occurs due to applied heat
Solution Approach 1:
By changing the temperature parameter to remain below 1200°C during application and service, the invention prevents diamond graphitization and degradation. The low-temperature binder system preserves the meta-stable diamond phase, maintaining ultra-hard properties while avoiding thermal damage that would occur with conventional high-temperature methods
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 solution provides a highly wear-resistant, dense, and economically viable coating that maintains the integrity of the steel substrate, with enhanced wear resistance comparable to the best commercially available thermally sprayed solutions, without the need for specialized equipment and with minimal substrate distortion.
Implementation Method 1
a wear-resistant layer metallurgically bonded to a surface of the body through an intermediate layer
Implementation Method 2
liquid-phase sintering. The sintering temperatures of the most commonly used WC—Co hard-metals are usually above the melting point of a eutectic temperature
Implementation Method 3
which allows the formation of a large fraction of liquid phase during sintering
Data Source
AI summary
The invention relates to a wear part or tool comprising a body containing an iron-group metal or alloy, a wear-resistant layer metallurgically bonded to a surface of the body through an intermediate layer, characterized in that the wear-resistant layer comprises at least 13 vol. % of grains of metal carbide selected from the group consisting of WC, TiC, VC, ZrC, NbC, Mo2C, HfC and TaC and grains of (Cr,Me)xCy and a metal based phase comprising of a solid solution of 0.5 to 20% Cr, 0.2 to 15% Si, and 0.2 to 20% carbon, where Me is Fe, Co and/or Ni; and the intermediate layer has a thickness of 0.05 to 1 mm and comprises Si in amount of 0.1 to 0.7 of that in the wear-resistant layer, chromium in amount of 0.1 to 0.6 of that in the wear-resistant layer and the metal of the metal carbide in amount of 0.2 to 0.6 of that in the wear-resistant layer and to a method of producing such a wear part.