Metal AM Winter 2015 by Inovar Communications

optimum processing conditions were characterised by good bonding, low dilution and were almost defect-free (occasionally a small spherical pore). The roughness of the side surface was significantly higher for the low alloy steel deposit. The average hardness of the low alloy steel after LMD was around 280 HV, while the X42Cr13 (‘hard’) steel resulted in a deposit with average hardness of 550-600 HV. As a reference, typical hardness values for conventionally manufactured 16MnCr5 gears are 350 HV in the core and 700 HV in the carburised surface layer. The results for tooth bending fatigue of the LMD gears are presented in Fig. 21. For parameter set 1, a higher bending strength during cyclic loading was obtained for the ‘hard’ steel than for the ‘soft’ low alloy steel. A slight improvement in bending strength was obtained for the gear consisting of the ‘soft’ steel in the core region and the ‘hard’ steel at the edges compared to the fully ‘soft’ steel gear. A significant improvement in bending strength was obtained by altering the processing conditions from parameter set 1 to parameter set 2, as a result of the absence of pores in the latter case. At optimum processing conditions, a fatigue bending strength of 800-850 MPa has been reached with the gear consisting completely of ‘hard’ steel. As a reference, case hardened 16MnCr5 steel has a bending stress of around 860 MPa. Gears, produced using parameter sets 1 and 2 and the hard steel powder, have been subjected to surface contact fatigue tests (see Fig. 22). All tests were stopped before failure occurred and before the normal ending of the test, in order to enable an intermediate evaluation of the gears. These tests indicate an allowable contact stress of around 1100 MPa. As a reference, an allowable contact of 1500 MPa can be expected from case hardened 16MnCr5 steel. The authors reached the final conclusions that the fatigue strengths, under bending and contact stress, already achieved have satisfied

Metal AM at Euro PM2015, Part 2

Fig. 22 Surface contact fatigue test results [6] the requirement for prototype gears, but that further analysis of the dynamic mechanical behaviour of gears, built using other powders and with additional heat treatments, is on-going.

Author David Whittaker DW Associates 231 Coalway Road, Wolverhampton WV3 7NG, United Kingdom Tel: +44 (0)1902 338498 Email: whittakerd4@gmail.com

References [1] H Brodin, Heat Treatment and Mechanical Testing of a Selective Melted Superalloy, as presented at Euro PM2015, Reims, France, October 4-7 2015. [2] P Vikner, R Giraud, C Mayer and M Sarasola, Towards Improved Quality and Production Capacity for Ni based Powders for Additive Manufacturing, , as presented at Euro PM2015, Reims, France, October 4-7 2015. [3] G Marchese, S Biamino, M Pavese, D Urgues, M Lombardi, P Fino and G Vallillo, Heat Treatment Optimization of Hastelloy X Superalloy Produced by Direct Metal Laser Sintering, , as presented at Euro PM2015, Reims, France, October 4-7 2015.

ink jet printing on a powder bed, , as presented at Euro PM2015, Reims, France, October 4-7 2015. [5] J Isaza, C Aumund-Kopp, S Wieland, F Petzoldt, M Bauschulte and D Godlinski, New Materials and Applications by 3D-Printing for Innovative Approaches, , as presented at Euro PM2015, Reims, France, October 4-7 2015. [6] M Rombouts, G Maes, F Varspringer and S Wilson, Process Development and Material Properties of Gears Manufactured by Laser Metal Deposition, as presented at Euro PM2015, Reims, France, October 4-7 2015.

World PM2016

In 2016, the Euro PM conference becomes the PM2016 Powder Metallurgy World Congress and Exhibition, taking place in Hamburg, Germany, October 9-13, 2016. The event will include a number of technical sessions focussed exclusively on metal AM. The PM world congress takes place every two years and rotates between Europe, Asia and North America. To find out more visit www.worldpm2016.com

[4] R Frykholm, B-G Andersson and R Carlstrom, Progress of precision

Metal Additive Manufacturing | Winter 2015