Research on Alloy 137 for Manual Surfacing of Valve Sealing Surfaces

Literature Overview

This paper, published in the journal Valve (1996, Issue 3) by Gao Qingbao, Li Jiajie, and Yu Dechun from the Shenyang Valve Research Institute, reports on the development and validation of a manual surfacing alloy designated as Alloy 137 for valve sealing surface applications. The research demonstrates that Alloy 137 outperforms conventional 2Cr13 and Alloy 85 in terms of sealing performance and durability for high and medium pressure valves operating below 450°C in oil, steam, and water service. This work represents an important contribution to the field of valve engineering and surfacing technology.

Background and Technical Requirements

Valve sealing surfaces are subjected to severe mechanical and chemical demands, including cyclic contact stress, erosion, corrosion, and thermal cycling. The sealing surface material must provide adequate hardness for wear resistance, sufficient ductility to conform to the mating surface, and corrosion resistance against the process medium. Traditional materials such as 2Cr13 (a martensitic stainless steel) and Alloy 85 (a nickel-based alloy) have been widely used but exhibit limitations in certain service conditions.

The development of Alloy 137 was driven by the need for a cost-effective, readily available surfacing material that could meet or exceed the performance of existing alternatives in the target service range. The alloy was specifically formulated for manual arc welding surfacing (SMAW), which is the most common method for valve sealing surface repair and fabrication in Chinese industrial practice.

Performance Evaluation Methodology

The performance of Alloy 137 was evaluated through a combination of laboratory testing and industrial field trials. The laboratory testing included hardness measurements, wear resistance tests, and corrosion resistance evaluations. The industrial field trials involved installing valves with Alloy 137 surfaced sealing surfaces in actual service conditions and monitoring their performance over extended operating periods.

The comparison with 2Cr13 and Alloy 85 was conducted under identical test conditions to ensure a fair and objective assessment. The key performance indicators included sealing integrity, leakage rate, service life, and resistance to galling and scoring. The field trial data provided the most convincing evidence of Alloy 137's superiority, as it demonstrated performance in real operating conditions rather than idealized laboratory environments.

Technical Characteristics and Advantages

Alloy 137 offers several advantages over its predecessors. The improved hardness provides better resistance to abrasive wear and galling, which are common failure modes in valve sealing surfaces. The optimized composition provides enhanced corrosion resistance in oil, steam, and water environments, extending the service life of the valve. The alloy's compatibility with manual arc welding surfacing makes it accessible to a wide range of valve manufacturers and maintenance workshops.

The service temperature limit of 450°C is a defining characteristic of Alloy 137, which positions it as a suitable choice for a broad range of industrial valve applications including steam systems, water systems, and oil processing equipment. Above this temperature, the alloy may experience accelerated oxidation or softening, which would compromise its sealing performance.

Engineering Practice and Application Guidance

The application of Alloy 137 in valve manufacturing requires adherence to proper surfacing practices. The base metal preparation is critical, with adequate surface cleaning and preheating to prevent cold cracking and ensure proper fusion. The surfacing parameters, including current, voltage, travel speed, and interpass temperature, must be carefully controlled to achieve the desired microstructure and mechanical properties.

For high-pressure valves, multiple surfacing passes may be required to build up the sealing surface to the specified thickness and profile. The final surface finish should be machined or ground to achieve the required surface roughness for optimal sealing performance. The transition zone between the Alloy 137 surfacing layer and the base metal should be examined for any cracks or lack of fusion defects.

Key Questions and Reflections

While the study provides convincing evidence of Alloy 137's superior performance, several aspects warrant further investigation. The long-term creep behavior and thermal fatigue resistance of Alloy 137 under cyclic thermal loading conditions are not addressed. The alloy's performance in more aggressive environments, such as those containing chlorides or acidic compounds, should be evaluated. Additionally, the effect of welding parameters on the microstructure and properties of Alloy 137 surfacing layers would provide valuable guidance for optimizing the welding process.

The availability and cost-effectiveness of Alloy 137 compared to Alloy 85 should be considered in the broader economic context of valve manufacturing. If Alloy 137 offers comparable performance at a lower cost, it could significantly reduce the total cost of ownership for valve systems.

Summary and Conclusions

This study establishes Alloy 137 as a viable and superior alternative to 2Cr13 and Alloy 85 for manual surfacing of valve sealing surfaces in high and medium pressure applications below 450°C. The combination of laboratory testing and industrial field trials provides robust evidence of the alloy's improved performance in terms of sealing integrity, wear resistance, and corrosion resistance. The alloy's compatibility with manual arc welding surfacing ensures broad accessibility for valve manufacturers and maintenance operations. The research contributes to the ongoing development of specialized surfacing alloys for critical valve applications and demonstrates the value of systematic material development and validation in improving industrial equipment reliability.