PM²TEC 2001, in New Orleans, USA. Authors: John McLelland, Owe Mårs, Thomas J. Jesberger. It is well known that the cooling rate influences the final microstructure and therefore the properties of sinter hardened steel parts. This investigation looked at the relationship between the sintering furnace cycle (time, temperature and atmosphere) and cooling rate to part microstructure. The objective was to identify how the above sintering variables influenced the development of martensite, hardness and strength. Tests were conducted varying the sintering cycle. The changes to the cycle were sintering time, sintering temperature, atmosphere composition (specifically hydrogen concentration), and cooling rate. The final microstructure was evaluated and correlated to the sintering cycle.