Low-Chromium Hardfacing Alloys Using Transition Metal Borides
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Solution Overview
Problem
Chromium-bearing alloys used in wear-resistant applications release carcinogenic hexavalent chromium fumes during casting or welding, exceeding regulatory standards, necessitating the development of chromium-free or low-chromium alternatives that maintain wear resistance.
Innovation Solution
Development of low or chromium-free ferrous alloys with a total mole fraction of transition metal borides and borocarbides greater than or equal to 5 wt%, where the metallic component comprises greater than 15 wt% Ti+W+Mo+V, and a hardness of at least 55 HRC, achieved through specific alloy compositions and processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium-bearing alloys are used to achieve wear resistance, then wear performance is improved, but carcinogenic hexavalent chromium fumes are released exceeding regulatory standards
Solution Approach 1:
The patent removes chromium from the alloy composition entirely, extracting the harmful element while maintaining wear resistance through alternative mechanisms. The alloy uses transition metal borides and borocarbides (containing Ti, W, Mo, V) to provide wear resistance without chromium, thereby eliminating hexavalent chromium fume generation during casting or welding operations
Solution Approach 2:
The patent changes the chemical composition parameters by specifying a total mole fraction of transition metal borides and borocarbides ≥5 wt% with metallic component comprising ≥15 wt% Ti+W+Mo+V, and achieving hardness ≥55 HRC. These parameter changes enable chromium-free wear-resistant material that meets regulatory standards
2Reliability
If high chromium content is used to improve hardenability and form chromium containing carbides and borides, then wear performance is enhanced, but chromium emissions increase
Solution Approach 1:
The patent extracts chromium from the alloy system and replaces it with transition metals (Ti, W, Mo, V) that form borides and borocarbides. This substitution eliminates the source of chromium emissions while maintaining the hardening mechanism through alternative intermetallic phases
Solution Approach 2:
The patent creates a composite alloy system combining multiple transition metals (Ti, W, Mo, V) with boron and carbon to form a complex mixture of borides, borocarbides, and isolated carbides. This composite approach provides wear resistance through diverse hard phases without relying on chromium
Data Source
AI summary
Disclosed herein are embodiments of hardfacing/hardbanding materials, alloys, or powder compositions that can have low chromium content or be chromium free. In some embodiments, the alloys can contain transition metal borides and borocarbides with a particular metallic component weight percentage. The disclosed alloys can have high hardness and ASTM G65 performance, making them advantageous for hardfacing/hardbanding applications.