Case History: SECO/WARWICK High Volume Gas Nitriding and Ferritic Nitrocarburizing System for Heat Treating at a Much Lower Cost.

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Nitrocarburizing system with 6 horizontal retort furnaces connected by an automatic handling system.

SECO/WARWICK designed and built six batch retort gas nitriding furnaces using the ZeroFlow process with vacuum purge and other components for an automated production line for heat treating various sizes of gears. In addition to the large-size horizontal retort furnaces, SECO/WARWICK provided a four-chamber vacuum washer, two furnaces for pre-oxidizing, a post-heat treatment cooling station, and a robotic system for loading and unloading.

The entire system has been installed and is producing gears at full capacity while meeting stringent automotive production requirements. The goal of nitrocarburizing a million gears a year is being met with 99% processing repeatability, 98% uptime, and a single maintenance break in the last year.

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Process-gas consumption for nitriding at 530°C and creating a gamma prime + alpha layer.

Per a case study, after nitrocarburizing the gears achieved quoted specification requirements for the nitrided (nitrocarburizing) thickness and hardness, structure of the compound layer, and porosity. No deficient gears were found during normal production, and fatigue properties improved by nearly 50%.

Heat treating costs also reached an 80-percent reduction in amount of ammonia used compared to the previous system (from over 350,000 lbs/yr to 44,000 lbs/yr), while only 1 m³ of methanol completely replaced all methane and propane previously used to supply the carbon (as well as fuel).

In total, unit costs of gas nitriding (ferritic nitrocarburizing) with the ZeroFlow process were cut substantially by using the automated front-loading batch furnaces and handling system compared to the previous continuous furnace, while completely removing environmental and safety hazards by eliminating all previous issues of polluting (NOx) gas emissions.