Nitrided Track Pin for Galling Resistance
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Solution Overview
Problem
Track chain assemblies in track-type machines face galling failures due to high contact stresses at the bearing interface between track pins and bushings, limiting their lifespan, and existing solutions like hard coatings or nitriding either fail to provide sufficient strength or are costly and inefficient.
Innovation Solution
A track pin made from a steel alloy with a nitride-forming element and silicon, subjected to hot deformation, quenching, tempering, and nitriding to create a hard nitrided surface, maintaining core strength and providing a dissimilar microstructure to the bushing for improved galling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hard coatings (PVD or CVD) are applied to pins to improve galling resistance, then galling resistance is improved, but manufacturing cost increases and adherence becomes problematic
Solution Approach 1:
The patent changes the material parameters by using nitriding alloy steel with specific composition (1.0-3.0% Si, 0.26-0.37% C, 1.5-2.5% Cr, 0.3-1.0% Mo) and controlling nitriding parameters (temperature 400-600°C, time 1-24 hours) to create a hard nitrided surface layer with dissimilar microstructure to the bushing, achieving galling resistance through material parameter optimization rather than external coatings
Solution Approach 2:
The patent creates a composite structure within the pin itself through nitriding, forming a hard nitrided surface layer (comprising nitride phases) over a tempered martensitic core, creating a composite material structure that provides both wear resistance and strength without requiring external coatings
2Reliability
If nitriding is applied to create a hard surface case, then surface hardness and galling resistance are improved, but core strength is reduced due to high processing temperatures
Solution Approach 1:
The patent modifies the steel composition parameters by adding 1.0-3.0% Si and 1.5-2.5% Cr to create a nitriding alloy that can withstand nitriding temperatures (400-600°C) without excessive strength loss, and uses controlled nitriding parameters to achieve optimal case hardness while preserving core integrity
Solution Approach 2:
The patent applies local quality by creating a nitrided surface layer with dissimilar microstructure to the core through controlled nitriding, where the surface region (case) has different properties (harder, more wear resistant) than the core, allowing each region to optimize for its specific function
3Reliability
If track pin size is increased to increase surface contact area and decrease contact stresses, then galling propensity is reduced, but system cost increases due to disproportionate increases in all related components
Solution Approach 1:
The patent changes the material parameters of the track pin through nitriding, creating a hard surface layer that reduces galling resistance requirements, thereby allowing the use of standard-sized pins without increasing contact area, thus avoiding the cost increase associated with larger components
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 nitrided track pin achieves superior galling resistance and strength, extending the service life of track chain assemblies while maintaining core strength, and reducing system costs by avoiding the need for larger components.
Implementation Method 1
nitriding the track pin to form an external nitrided surface
Implementation Method 2
quenching and tempering the steel alloy to a specific core hardness
Data Source
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AI summary
A track pin (80, 180) for a track chain assembly (16) includes a body (120, 220) made from a steel alloy. The steel alloy has a composition comprising iron, a nitride-forming element, and silicon. The composition of the steel alloy comprises at least 0.5 percent by weight of silicon. The body (120, 220) includes an external nitrided surface (125, 225).