In this study, amorphous calcium phosphate ceramic (ACP) was employed in plasma spray onto stainless-steel metal surface under different controlled atmospheres of Ar H2 and Ar N2. A commercial hydroxyl apatite (CHA) was plasma-sprayed for the purpose of comparison. Results showed that the plasma-sprayed ACP coating is primarily a mixture of a crystalline carbonate-containing apatite phase with considerable amounts of Ca4P2O9, and trace amounts of α-tricalcium phosphate. However, a predominantly highly crystalline hydroxyl apatite (HAp) with small amounts of impurities was formed for the CHA coating. No considerable difference in coating constituents (phases) and microstructure was found between coatings formed under the two plasma gases. The ACP coating exhibit high porosity, leading to weaker interfacial strength, while the CHA coating shows dense packing. However, the absence of detectable microcracks in the ACP coating suggests its potential application for biomedical purposes.