Low-Crystallinity Chromium Plating for Fracture-Resistant Polishing
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Solution Overview
Problem
Chromium-plated films deposited from trivalent chromium baths are prone to brittle fracture during polishing, which is a problem in the manufacturing of plated members like rods used in sliding components.
Innovation Solution
A plated member with a chromium-plated film composed of 60 to 80% chromium, 16.5 to 30% carbon, and an indentation hardness of 7 GPa or more, and a degree of crystallinity of 4% or less, formed using a trivalent chromium bath, to reduce the likelihood of tearing fractures during polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a plated film is deposited from a conventional trivalent chromium bath, then environmental sustainability is improved compared to hexavalent chromium, but the plated film becomes susceptible to brittle fracture during polishing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the trivalent chromium bath (specific chromium concentration, additive types and concentrations) and deposition parameters (current density, temperature, pH) to produce a plated film with optimized microstructure that resists brittle fracture while maintaining environmental safety
Solution Approach 2:
The patent creates a composite structure within the plated film by incorporating specific organic additives and their decomposition products along with chromium, forming a composite material with enhanced mechanical properties that prevents brittle fracture during polishing operations
2Strength
If the chromium content in the plated film is increased to improve wear resistance, then sliding characteristics are improved, but the film becomes more brittle and prone to tearing fractures
Solution Approach 1:
The patent optimizes the chromium content parameter within a specific range (60-80 at%) rather than maximizing it, and balances it with controlled amounts of carbon (16.5-30 at%) and oxygen (2-6 at%), achieving both wear resistance and fracture resistance through parameter optimization
Solution Approach 2:
The patent creates a composite plated film structure where chromium provides wear resistance while incorporated organic compounds and their decomposition products enhance toughness and prevent brittle fracture, achieving synergistic properties
3Strength
If the plated film is made harder to improve wear resistance, then sliding characteristics are improved, but the film generates abrasive marks during polishing
Solution Approach 1:
The patent controls the hardness parameter within an optimal range (5-15 GPa) rather than maximizing it, and correlates this with controlled carbon content (16.5-30 at%) to achieve a balance between wear resistance and polishability, preventing excessive hardness that would cause abrasive marks
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 plated member with a chromium-plated film that is less susceptible to tearing fractures during polishing, maintaining environmental sustainability and ensuring excellent sliding characteristics and wear resistance.
Implementation Method 1
a plated film mainly composed of chromium deposited from a trivalent chromium bath
Implementation Method 2
the indentation hardness indicates a value obtained by instrumented indentation hardness measurement using a nanoindentation method
Implementation Method 3
a degree of crystallinity calculated from a peak integrated intensity ratio of a measured value of X-ray diffraction measurement
Data Source
AI summary
The present plated member includes, on an outer surface, a plated film mainly composed of chromium deposited from a trivalent chromium bath containing at least chromium, carbon, and oxygen, in which the plated film contains 60 to 80 at % of chromium and 16.5 to 30 at % of carbon and has an indentation hardness of 7 GPa or more on the outer surface, and a degree of crystallinity calculated from a peak integrated intensity ratio of a measured value of X-ray diffraction measurement and the following expression (1) is 4% or less.