Composite CVJ Inner Race With Zoned Hardness for Wear and Machining
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Solution Overview
Problem
Conventional manufacturing processes for torque transfer parts like bevel gears and constant velocity joints in vehicle wheel drive lines face challenges in achieving desired mechanical properties, such as enhanced tooth wear and fatigue strength, while maintaining dimensional precision and surface finish, due to uniform case depth and hardness issues.
Innovation Solution
A method of creating forged composite powder metal parts using at least two different powder metal materials, where one material forms the outer surface and another forms the pre-forged core, allowing for varying hardness properties and profiles through sintering and forging, enabling specific features like ball tracks and splines to be optimized for their respective demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a uniform case depth is achieved through case carburizing, then the gear teeth have enhanced wear and fatigue strength, but the spline area becomes difficult to machine with required dimensional tolerances
Solution Approach 1:
The patent applies local quality by creating a non-uniform case depth distribution where the gear teeth receive a deeper case (0.040-0.060 inches) for enhanced wear and fatigue strength, while the spline area receives a shallower case (0.015-0.030 inches) that maintains dimensional precision and machinability. This is achieved through selective masking during case carburizing or by using different powder metal materials with varying hardenability in different regions of the part.
2Strength
If a deep hardened area is provided in ball tracks to prevent wear and spalling, then load bearing capacity is improved, but the overall part hardness becomes excessive for cost-effective machining
Solution Approach 1:
The patent applies local quality by providing a deeper case depth (0.040-0.060 inches) specifically in the ball track regions to enhance load bearing capacity and prevent wear, spalling, and brinnelling, while maintaining a shallower case depth (0.015-0.030 inches) in other areas like the spline regions. This localized hardening approach allows the ball tracks to have the necessary hardness for high contact stress applications while keeping other areas softer and more machinable.
3Adaptability or versatility
If different material properties are required in different regions of the part, then performance requirements are optimized, but a single material composition cannot satisfy conflicting requirements
Solution Approach 1:
The patent applies composite materials by creating a multi-material powder metal part where different regions contain different base materials with varying hardenability. For example, the gear tooth regions may use a high-carbon steel powder (0.5-1.0% C) that hardens to 58-64 HRC, while the spline regions use a lower-carbon steel powder (0.15-0.40% C) that hardens to 48-54 HRC. This allows each region to have material properties optimized for its specific functional requirements.
4Device complexity
If conventional case carburizing is used to achieve uniform hardness, then processing is simplified, but secondary operations are required to achieve dimensional accuracy
Solution Approach 1:
The patent applies preliminary action by forming the composite preform compact with pre-defined material distribution and preliminary geometry before case carburizing. The green compact is shaped with near-net dimensions and material zones are pre-positioned, so that after sintering and case carburizing, the part achieves both dimensional accuracy and the desired non-uniform case depth distribution, minimizing or eliminating the need for secondary machining operations.
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
This approach allows for the creation of parts with tailored material properties, eliminating conflicts between feature requirements, achieving improved wear resistance, impact resistance, and machining ease, while minimizing the need for secondary operations and reducing costs.
Implementation Method 1
The composite preform compact is sintered and forged to form the forged composite powder metal part
Implementation Method 2
The composite preform compact is sintered and forged to form the forged composite powder metal part
Data Source
AI summary
A forged composite inner race for a constant velocity joint is forged from a composite preform compact including a first powder metal material and a second powder metal material. The forged composite inner race includes a plurality of ball tracks formed on an outer section of the forged composite inner race with corresponding lands between adjacent ball tracks and an axially-extending splined opening formed in an inner section of the forged composite inner race. The outer section comprises the first powder metal material in a higher concentration than the second powder metal material and the inner section comprises the second powder metal material in a higher concentration than the first powder metal material.