Study on the microstructure, mechanical properties and cavitation erosion resistance of 17-4PH alloy coatings fabricated by high power laser cladding

Abstract

The high power laser cladding (HPLC) process with laser power of 15 kW was used for the first time to fabricate 17-4PH alloy coatings. The build rate of the HPLC process reached 272 mm³/s, markedly surpassing that of conventional low power laser cladding process (≤85 mm³/s). Subsequently, the microstructure and mechanical properties of the coatings at different aging temperatures (300–550 °C) was characterized. Moreover, with increasing aging temperature, the hardness, strength and plasticity of 17-4PH coting initially ascend before descending. At 480 °C, due to the remarkably high martensite content and the optimal synergy between the size and quantity of ε-Cu precipitates, the break elongation (19.5 ± 0.5 %) achieved its zenith, which is at the highest level in existing reports. The hardness (436 ± 5 HV) and ultimate tensile strength (1218 ± 8 MPa) have also reached the level of low power laser cladding process. Finally, the results of the cavitation erosion resistance (CER) testing indicate that the CER of the 17-4PH coating aged at 480 °C in deionized water is 2.4 times that of the 0Cr13Ni5Mo substrate. High hardness and elastic-plastic capability of the 17-4PH coating are the key factors for higher CER than the substrate. The 17-4PH coatings crafted by HPLC not only has higher efficiency, but also obtains remarkable mechanical performance and CER, which may provide a promising solution for surface strengthening or repair of hydroelectric power equipment such as Pelton runners.