Low coefficient of thermal expansion (CTE) Fex-Ni1-x alloys could be used as functional or structural materials for many applications requiring high dimensional stability with temperature especially in the field of miniaturised components. Metal (MIM) and Micro metal injection moulding (?MIM) emerges as a cost effective methods for fabricating parts thereof. Low CTE Fex-Ni1-x alloys are sensible of elements contamination during the debinding and sintering stages and their dimensional stability could be affected. The present work studies the effect of using different debinding and sintering atmospheres in the ?MIM process of Invar 36 feedstocks based on cellulose acetate butyrate (CAB) binders. Sinterability, microstructures and compositional studies were carried out to determine the effectiveness of each combination of processing atmospheres which includes vacuum or air for debinding and vacuum or hydrogen for sintering. Several combinations of temperature and atmospheres lead to proper densification and desirable austenitic microstructure responsible of the low CTE of Invar 36 alloy.