The production process for powdered metal parts can be greatly enhanced by precisely controlling the chemical carbon potential of the sintering atmosphere.

This is the focus of a paper to be presented by Linde engineers at PowderMet 2012 sponsored by the 2012 International Conference on Powder Metallurgy and Particulate Materials, to be held from June 10th to 13th at the Gaylord Opryland Hotel in Nashville, Tennessee.

The paper, entitled, Improved Quality by Carbon Potential Control in Metal Injection Molding Sinter Furnace Atmospheres, will be presented by Tony Palermo, Metallurgy Program Manager for Linde in North America, and Akin Malas, Head of Heat Treatment Industry Segment, also from Linde.

The paper describes a means to control the chemical carbon potential of the sintering atmosphere in order to produce higher quality product while, in effect, lowering the cost of production, enhancing customer satisfaction, and expanding the current and future market penetration of parts produced by metal injection molding and powder injection molding.

“There are a number of practices which, if not controlled properly, may contribute to the generation of defects or insufficient sintered part properties or appearance, which reduce quality, increase costs, and lead to dissatisfied customers and, ultimately, diminished market share,”

Palermo points out in his paper.

“We have found that one of the root causes of these problems resides in the surface decarburisation or carburisation of the sintered parts which may be the result of carbon potential fluctuation in the sintering process.”

The problem can be eliminated by using the Linde Sinterflex® control system to precisely manage and control the carbon potential in the furnace throughout the sintering process.

The new technology uses continuous atmosphere sampling, a proprietary oxygen probe, and a carbon monoxide analyser to continuously calculate atmosphere carbon potential and provide the addition, when needed, of an appropriate trim gas mixture to maintain carbon potential within a desired, pre-set range.

“The objective of this technology is to maintain a furnace atmosphere carbon potential that contributes to the processing of sintered parts that meet required, or desired, carbon composition and consequent properties,” Palermo said.