Numerical and Experimental Analysis of the Gear Size Influence on Density Variations and Distortions during the Manufacturing of PM Gears with an Innovative Powder Processing Route Incorporating HIP

Arne Melander,Alireza Khodaee

doi:10.3390/jmmp2030049

Abstract

The paper is the result of research intended to develop a process route for the manufacturing of powder metallurgical (PM) gears for application in transmissions units for heavy duty powertrain applications. The main problem of PM for such applications is that the generated pores that occur through conventional pressing and sintering processes reduce the gear strength, which reduces the capacity for power transmission by the gear. In prior work, removing the pores and reaching 100% density by adding Hot Iso-static Pressing (HIP) after two times pressing and two times sintering steps in the process route was suggested to solve the mentioned problem. During the investigations of this work it was revealed that the gear dimensions could influence the process results with respect to geometrical distortions. In this paper we have presented a finite element (FE) model based analysis on how the gear geometrical parameters influenced the distortions occurring in HIP. The simulation model is validated with experiments. Furthermore, the simulation model is used to create a prediction model for further investigations. The research showed that PM gears with different sizes during the proposed process route behaved differently in terms of distortions. This was illustrated with a series of simulations with different gear geometries. A regression model was developed based on the FE results for further practical predictive use. The distortions caused by HIP should be considered in the process design to prevent expensive post processes afterwards to reach the gear with accurate geometry and keep the costs of manufacturing low. It is concluded that it is possible to use the innovative process route including HIP to reach the full density and close all the open pores but not for all kind of gear geometries.

Highlights

Powder metallurgical (PM) gears offer a number of benefits, which make them a sustainable alternative to the traditional gears made of wrought steel by conventional manufacturing processes.Among all of the advantages for powder metallurgical (PM) gears, lower cost of production, lower amount of material waste in manufacturing, and the possibility to add new design features to the shape of the gear are the most mentioned advantages by PM researchers in the literature [1,2,3,4].The lower density of PM gears manufactured by pressing-sintering process routes limits their applications for higher load transmission duties [5]
The gearThe sizeresults effectsare since allon other in the distortions for a range of gear geometries the based the variants measurements two are similar. and
The first is to find out the potential relation between the distortions caused by Hot Iso-static Pressing (HIP) and the lowest relative density in the gear neutral zone (RDmin )

Summary

Introduction

Powder metallurgical (PM) gears offer a number of benefits, which make them a sustainable alternative to the traditional gears made of wrought steel by conventional manufacturing processes. The lower density of PM gears manufactured by pressing-sintering process routes limits their applications for higher load transmission duties [5]. For such applications the full strength of steel is. 2018, 2, 49; doi:10.3390/jmmp2030049 www.mdpi.com/journal/jmmp sintering process route followed by a container-less HIP densification at the end [9]. In this process full density can be achieved [10,11].

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Results

Discussion

Conclusion