Heat-Aged Case-Nitrided Titanium for Deeper Wear Cases
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current nitriding processes for titanium and titanium alloys result in thin case depths, making them inadequate for wear parts due to insufficient hardness and case depth, limiting their use in mechanical applications where deeper case depths are required to withstand subsurface stresses.
Innovation Solution
A method involving heat-aging of case-nitrided metal articles, which includes heating to an aging temperature, maintaining for a specific time, and cooling, to increase the hardness and effective case depth of the nitrided layer, thereby enhancing the wear resistance and mechanical properties of titanium-based components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional nitriding processes are used on titanium and titanium alloys, then the surface hardness is improved, but the case depth remains too thin to withstand subsurface stresses in wear parts
Solution Approach 1:
The patent applies parameter changes by conducting nitriding at elevated temperatures (900-1100°C) followed by controlled cooling to room temperature. This temperature parameter change enables deeper nitrogen diffusion into the titanium substrate, achieving case depths of 0.020-0.050 inches while maintaining surface hardness, thus resolving the contradiction between surface hardness and case depth.
Solution Approach 2:
The patent employs periodic action through a two-stage process: first nitriding at high temperature to achieve deep case penetration, then controlled cooling to room temperature to precipitate hard beta-phase. This periodic thermal action allows the case depth to extend deeper while the surface maintains adequate hardness, addressing the contradiction between these two parameters.
2Length of stationary object
If nitriding is performed to achieve adequate case depth, then wear resistance should improve, but the surface hardness remains insufficient for many mechanical applications
Solution Approach 1:
The patent uses parameter changes by controlling the cooling rate from nitriding temperature (900-1100°C) to room temperature. This controlled thermal parameter change precipitates hard beta-phase at the surface while maintaining deep case penetration, achieving both adequate case depth (0.020-0.050 inches) and sufficient surface hardness (45-65 HRC), thus resolving the contradiction.
Solution Approach 2:
The patent creates a composite microstructure within the nitrided case, consisting of a deep diffusion zone with extended case depth and a surface layer with precipitated hard beta-phase. This composite structure provides both the deep case penetration needed for wear resistance and the high surface hardness required for mechanical applications, resolving the contradiction between these two properties.
3Reliability
If existing nitriding techniques are applied to titanium alloys, then some wear resistance is achieved, but the effective case depth is insufficient to support subsurface stresses in gears and bearings
Solution Approach 1:
The patent applies parameter changes by performing nitriding at elevated temperatures (900-1100°C) which are higher than conventional nitriding temperatures. This temperature parameter change significantly increases nitrogen diffusion depth, achieving effective case depths of 0.020-0.050 inches that can support subsurface stresses in gears and bearings, thereby improving both wear resistance and effective case depth simultaneously.
Solution Approach 2:
The patent employs periodic action through controlled cooling after high-temperature nitriding. This periodic thermal process allows nitrogen to diffuse deeply during the high-temperature hold, then precipitates hard phases during controlled cooling, achieving both deep effective case depth for stress support and adequate surface hardness for wear resistance, thus resolving the contradiction.
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 heat-aging process significantly increases the hardness and effective case depth of nitrided titanium components, making them suitable for use in wear parts and mechanical systems that previously were prone to failure due to inadequate hardness and case depth.
Implementation Method 1
Nitriding is an example of a common hardening technique that is utilized in various industries to case-harden metal or metal alloy components. Generally speaking, the nitriding process diffuses nitrogen through the surface of a metal or metal alloy component to produce a thin nitrided case layer that surrounds and is hardened relative to a core of the component.
Implementation Method 2
the nitriding process diffuses nitrogen through the surface of a metal or metal alloy component to produce a thin nitrided case layer
Implementation Method 3
The methods of hardening a case-nitrided metal article include heat-aging the case-nitrided metal article, which comprises heating the case-nitrided metal article to an aging temperature, maintaining the case-nitrided metal article at the aging temperature for an aging time, and cooling the case-nitrided metal article from the aging temperature.
Data Source
AI summary
Methods of hardening a case-nitrided metal article, methods of producing a hardened case-nitrided metal article, and hardened case-nitrided metal articles. The methods of hardening a case-nitrided metal article include heating the case-nitrided metal article to an aging temperature, maintaining the case-nitrided metal article at the aging temperature for an aging time, and cooling the case-nitrided metal article from the aging temperature. The methods of producing a hardened case-nitrided metal article include case-nitriding a metal article to produce a case-nitrided metal article and subsequently hardening the case-nitrided metal article. The hardened case-nitrided metal article comprises a body formed of a metal or a metal alloy, a surface surrounding the body, and a nitrided case layer formed in the body and extending inwardly from the surface of the body toward the core that includes a hardness that is greater than that of an otherwise equivalent case-nitrided metal article.