Piston Ring Coating Composition for Wear Without Cracking
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Solution Overview
Problem
Current sliding members, such as piston rings for internal combustion engines, face challenges in achieving adequate wear resistance and toughness, especially under severe conditions associated with weight saving and increased output, and are susceptible to cracking and peeling when used in alcohol fuel vehicles.
Innovation Solution
A sliding member with a Cr-B-Ti-V-(Mn, Mo)-N-based alloy film is developed, containing Mn and Mo in a total content of 2 mass% or less, with specific ranges for B, V, and Ti, and an optional nitriding treatment layer or metal underlayer, providing a hard carbon film for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard film is formed on the outer peripheral sliding surface to improve wear resistance, then wear resistance is improved, but the film is susceptible to cracking and peeling under severe conditions
Solution Approach 1:
The patent changes the chemical composition parameters of the wear-resistant film by adding Mn and Mo elements to the Cr-B-Ti-V-N base composition. This parameter modification optimizes the film's toughness and adhesion properties, preventing cracking and peeling while maintaining wear resistance under severe conditions including alcohol fuel environments.
Solution Approach 2:
The patent creates a composite wear-resistant film by combining multiple elements (Cr, B, Ti, V, Mn, Mo, and N) in specific proportions. This composite structure integrates the hardness-providing elements (Cr, Ti, V) with the toughness-enhancing elements (Mn, Mo), achieving both wear resistance and resistance to cracking/peeling simultaneously.
2Productivity
If the piston ring is designed for weight saving and increased output, then engine performance is improved, but the sliding member operates under more severe conditions requiring higher toughness
Solution Approach 1:
The patent modifies the compositional parameters of the coating film by incorporating Mn and Mo elements with controlled content ranges. This parameter optimization enhances the film's toughness and ductility, enabling the piston ring to withstand the severe mechanical stresses and thermal loads associated with high-output, weight-saving engine designs.
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 results in a sliding member with low friction and excellent toughness, reducing the likelihood of adhesion, cracking, and peeling, and is applicable under severe conditions, including those involving alcohol fuels, while maintaining wear resistance and peeling resistance.
Implementation Method 1
a hard film formed by a physical vapor deposition (PVD) method
Implementation Method 2
a nitrided layer
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
To provide a sliding member, such as a piston ring for an internal combustion engine, having low friction and excellent toughness. The above-described problem is solved by a sliding member (10) such as a piston ring coated with a Cr-B-Ti-V-(Mn, Mo)-N-based alloy film (2) on a sliding surface (11) thereof, and configured so that the alloy film (2) contains one or both of Mn and Mo and has a total content of the Mn and the Mo within a range of 2 mass% or less. Preferably, a B content is within a range of 0.1 mass% to 1.5 mass%, inclusive, a V content is within a range of 0.05 mass% to 1 mass%, inclusive, and a Ti content is within a range of 0.05 mass% to 1.5 mass%, inclusive.