Sulphonitriding Piston Ring for Scuffing Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piston rings in internal combustion engines face challenges with scuffing and wear resistance, particularly in flex-fueled vehicles where the combustion strategy and fuel mixtures lead to reduced oil film thickness, causing increased contact between mating surfaces and resulting in scuffing, despite existing surface treatments like nitriding, oxynitriding, and ceramic coatings which have limitations in durability and adhesion.
Innovation Solution
A sulphide rich compound layer with an iron nitride matrix and iron sulphide inclusions is formed on the piston ring surface, with specific sulphur and nitrogen content, providing improved scuffing and wear resistance through reduced friction coefficient and enhanced lubrication properties, using the sulphonitriding technology to control the phase composition and structure of the treated layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If gas nitriding is applied to increase surface hardness and wear resistance, then scuffing resistance improves, but the surface becomes prone to scuffing under severe conditions with thin oil film
Solution Approach 1:
The invention creates a composite surface layer through sulphonitriding that combines iron sulphide (FeS) inclusions within an iron nitride matrix. This composite structure provides both the hardness of nitride phases and the low friction/lubrication properties of sulphide phases, resolving the contradiction between hardness and scuffing resistance
Solution Approach 2:
The invention changes the chemical composition parameters by introducing sulphur (1-4 wt%) in addition to nitrogen (10-20 wt%) during the heat treatment process. This parameter change transforms the surface layer from a pure nitride structure to a sulphonitride composite, enabling simultaneous achievement of hardness and scuffing resistance
2Reliability
If oxynitriding with oxide layer is applied to reduce friction coefficient, then sliding function improves, but a porous rigid area develops that negatively influences operational behavior
Solution Approach 1:
The invention changes the chemical composition by using sulphur instead of oxygen to form the surface compound layer. FeS inclusions in the nitride matrix provide low friction without creating the porous rigid structure that occurs with oxide layers, thus maintaining both sliding function and structural stability
Solution Approach 2:
The FeS inclusions act as a sacrificial lubricating phase that can be consumed or transformed during operation, continuously providing low friction properties without compromising the underlying nitride matrix structure
3Strength
If diamond-like carbon coating is applied to improve wear resistance, then surface protection improves, but adhesion lacks when surface irregularities are fine
Solution Approach 1:
The FeS inclusions act as an intermediary phase between the iron nitride matrix and the external environment, providing a lubricating interface that reduces wear without requiring external coatings. The sulphide phase bonds well with the nitride matrix while providing superior tribological properties
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 sulphide rich compound layer effectively reduces scuffing and wear, maintaining performance under high load conditions and extreme temperatures, as demonstrated by Block-on-Ring and burning mark tests, where the sulphonitriding treated rings show superior resistance to scuffing and wear compared to nitrided and oxynitrided rings.
Implementation Method 1
Gas Nitrided Steel (GNS) is a common technology used for top rings in Otto engines. Gas nitriding is a case-hardening process whereby nitrogen is introduced into the surface of solid ferrous alloys by holding the metal at suitable temperature in contact with a nitrogen containing gas
Implementation Method 2
A sulphide rich compound layer with an iron nitride matrix and iron sulphide inclusions embedded in said matrix, said sulphide rich compound layer having a sulphur content of 1 to 4 wt % S and a nitrogen content of 10 to 20 wt % N
Implementation Method 3
The sulphide rich compound layer effectively reduces scuffing and wear, maintaining performance under high load conditions and extreme temperatures, as demonstrated by Block-on-Ring and burning mark tests, where the sulphonitriding treated rings show superior resistance to scuffing and wear compared to nitrided and oxynitrided rings
Data Source
AI summary
The present invention relates to a piston ring for an internal combustion engine, the piston ring comprises a sulphide rich compound layer forming a surface layer, said sulphide rich compound layer comprising an iron nitride matrix with iron sulphide (FeS) inclusions embedded in said matrix, said sulphide rich compound layer having a sulphur content of 1 to 4 wt % S and a nitrogen content of 10 to 20 wt % N.