Correlation of microstructure with hardness and wear resistance of stainless steel blend coatings fabricated by atmospheric plasma spraying

Correlation of microstructure with hardness and wear resistance of stainless steel (STS) blend coatings applicable to cylinder bores was investigated in the present study. STS 316 spray powders were mixed with 0, 10, 20, and 30 wt.% of Al2O3–ZrO2 powders, and then were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the coatings showed that iron oxides were formed in the austenitic matrix by oxidation during spraying for the STS 316 coating, while Al2O3–ZrO2 oxides were additionally formed in the matrix for the blend coatings. The hardness and wear test results revealed that the blend coatings showed the better hardness and wear resistance than the STS 316 coating, and that the hardness and wear resistance increased with increasing volume fraction of Al2O3–ZrO2 oxides. However, the main wear mode was changed from abrasive wear to delamination wear because of cracking of oxides and separation of oxide/matrix interfaces as the volume fraction of Al2O3–ZrO2 oxides increased. According to this change of the wear mode, the wear resistance of the blend coating containing very high volume fraction of Al2O3–ZrO2 oxides was not proportionally increased with the hardness increase.