20/20 is considered to be perfect vision, but the year 2020 outlook is quite obscure. We can view the current state of the PM industry through short-term, fear-tinted glasses or gain a clearer picture of long-range opportunities. Just like U.S. manufacturing in general, the PM industry has been impacted negatively by the pandemic.

Due to production by pressing and sintering, PM gears are porous. Since pores reduce the loaded area and are also probable crack initiators, the porosity determines the strength of the PM component. PM gears can be densified to increase their local density and, therefore, the load-carrying capacity. PM gears are compacted locally since they are mainly loaded directly at the surface. A common process to densify PM gears locally is the cold rolling process. The contact conditions in the cold rolling process determine the density profile and, therefore, the material properties of the PM component. The influence of the contact conditions in cold rolling of PM gears on the resulting density profile is yet to be investigated.

The properties of both shot-peened and cold rolled PM gears are analyzed and compared. To quantify the effect of both manufacturing processes, the tooth root bending fatigue strength will be evaluated and compared to wrought gears.

Powder metal (PM) gears normally sell due to the lower cost and their relatively high mechanical performance. The reason behind the lower cost is that most of the machining is omitted due to the net-shape forming process. So how net-shape are powder metal gears? In this article some hard-to-find information about the tolerances through the manufacturing steps will be presented.

Electrification has already started to have a noticeable impact on the global automotive industry. As a result, the drivetrains of hybrid (HEV) and full electric vehicles (EV) are facing many challenges, like increased requirements for NVH in high speed e-Drives and the need for performance improvements to deal with recuperation requirements. Motivated by the positive validation results of surface densified manual transmission gears which are also applicable for dedicated hybrid transmissions (DHTs) like e-DCTs, GKN engineers have been looking for a more challenging application for PM gears within those areas.

The heat treatment processing of powder metal (PM) materials like Astaloy requires four steps -- de-waxing, HT sintering, carburizing and surface hardening -- which are usually achieved in dedicated, atmospheric furnaces for sintering and heat treat, respectively, leading to intermediate handling operations and repeated heating and cooling cycles. This paper presents the concept of the multi-purpose batch vacuum furnace, one that is able to realize all of these steps in one unique cycle. The multiple benefits brought by this technology are summarized here, the main goal being to use this technology to manufacture high-load transmission gears in PM materials.

For metal replacement with powder metal (PM) of an automotive transmission, PM gear design differs from its wrought counterpart. Indeed, complete reverse-engineering and re-design is required so to better understand and document the performance parameters of solid-steel vs. PM gears. Presented here is a re-design (re-building a 6-speed manual transmission for an Opel Insignia 4-cylinder, turbocharged 2-liter engine delivering 220 hp/320 N-m) showing that substituting a different microgeometry of the PM gear teeth -- coupled with lower Young’s modulus -- theoretically enhances performance when compared to the solid-steel design.

This paper will provide examples of stress levels from conventional root design using a hob and stress levels using an optimized root design that is now possible with PM manufacturing. The paper will also investigate how PM can reduce stresses in the root from transient loads generated by abusive driving.

Except for higher-end gear applications found in automotive and aerospace transmissions, for example, high-performance, sintered-steel gears match wrought-steel gears in strength and geometrical quality. The enhanced P/M performance is due largely to advances in powder metallurgy over last two decades, such as selective surface densification, new materials and lubricants for high density and warm-die pressing. This paper is a review of the results of a decade of research and development of high- performance, sintered-steel gear prototypes.