Creep of High-Strength Steel Coated with Plasma Sprayed Self-Fluxing Alloy

This article compares the creep testing behavior of AISI 4340 high-strength steel in the as-received and coated conditions. The coating material used was a NiCrBSi self-fluxing alloy. The microstructural characterization was carried out using optical and scanning electron microscopy. The creep tests were conducted at a temperature of 550 °C and with loads of 200, 250, and 300 MPa. The microstructure analysis of the deposited layer revealed some inclusions, very low porosity, and good adhesion to the substrate. The results of the creep tests indicated a decrease in the time to rupture under loads of 250 and 300 MPa for the coated steel. At a load of 200 MPa, the coated steel presented longer times to rupture and higher yield strength, demonstrating an improvement over the uncoated steel under these test condition. The fracture surface inspection showed a failure by a ductile fracture in both samples, with and without coating.