Ferrous Base Material Coating for Plain Bearings
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Solution Overview
Problem
Plain bearings in reciprocating internal combustion engines, particularly in large two-stroke diesel engines, face issues with brittle fracture and cracking due to the formation of a thick, brittle FeSn2 connection zone between the ferrous base material and the white metal coating, leading to a short service life, even with attempts to minimize the FeSn2 layer thickness.
Innovation Solution
A layer system on the ferrous base material with a Sn-containing supporting part layer, where the connection zone essentially lacks FeSn2, achieved by controlling the thermal energy during the coating process to prevent martensite formation and using elements like P, As, Sb, Zn, Cu, and Ni to suppress FeSn2 formation, ensuring a strong metallurgical connection without brittleness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a white metal coating is alloyed onto the ferrous base material using conventional coating processes, then a metallurgical connection is formed, but a thick and brittle FeSn2 bonding zone is created leading to short service life
Solution Approach 1:
The patent applies parameter changes by precisely controlling the coating process parameters (temperature, time, alloy composition) to limit the formation of FeSn2 in the bonding zone to a maximum of 10 μm thickness. This involves optimizing the white metal coating composition and controlling the thermal energy input during coating to prevent excessive diffusion and formation of brittle FeSn2, thereby maintaining adhesive strength while eliminating brittleness and extending service life.
2Reliability
If the FeSn2 layer thickness is minimized to reduce brittleness, then cracking and brittle fracture are reduced, but the metallurgical connection strength is compromised
Solution Approach 1:
The patent optimizes parameter combinations including white metal coating composition (specific ratios of Sn, Pb, Cu, Zn, Sb), coating thickness, and thermal process parameters to achieve the optimal balance where FeSn2 is limited to ≤10 μm while maintaining strong metallurgical bonding. This involves precise control of cooling rates and thermal energy input to prevent both excessive FeSn2 formation and weak bonding.
3Stability of the object's composition
If centrifugal casting is used to apply the white metal coating, then the formation of a metal bath is prevented, but alloy component separation occurs during solidification leading to weakened connection areas
Solution Approach 1:
The patent modifies the white metal coating composition by adjusting the ratios of alloying elements (increasing Sn content, optimizing Pb, Cu, Zn, and Sb proportions) to control solidification behavior and prevent segregation of alloy components during centrifugal casting. This compositional optimization ensures homogeneous distribution of alloying elements and maintains strong connection between the coating and base material.
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 plain bearing with enhanced deformability and adhesive strength, eliminating the risk of brittle fracture and cracking, while maintaining a simple production process without new equipment, ensuring a longer service life and improved safety against failure.
Implementation Method 1
the support element layer is metallurgically bonded to the base material by a bonding zone, wherein essentially no FeSn2 is formed in the bonding zone
Implementation Method 2
controlling the thermal energy during the coating process to prevent martensite formation
Data Source
AI summary
A support element comprises a support metal layer (A) comprising a white metal-containing material preferably tin-containing material, and a base material layer (B), which are metallurgically connected using a adhesive layer which does not contain iron distannide. Independent claims are included for the following: (1) manufacture of support element; (2) sliding bearing; and (3) reciprocating internal combustion engine.