17-4PH steel is a precipitation-hardening stainless steel and is highly regarded due to its many applications. This alloy attracts many attentions in applications that need corrosion resistance in addition to high strength, and it is used in industries such as aerospace, marine, nuclear and chemical industries. selective laser melting as an additive manufacturing method is used to make metal parts directly from metal powder, in a layer by layer method, which uses a computerized design to create a 3D part. In this study, the microstructure, mechanical properties and corrosion properties of 17-4PH stainless steel made by selective laser melting method have been investigated and the target of this study is to modify the microstructure, improve the mechanical properties and corrosion properties of this stainless steel by heat treatment. Generally this stainless steel’s heat treatment includes two parts that they are solution annealing and precipitation hardening. This study tries to improve its properties by designing heat treatment cycles and investigating the effect of each heat treatment parameters. Microstructural observations, EBSD data and eva‎luation of the initial powder’s chemical composition showed that selective laser melting cause to achieve δ ferrite microstructure. annealing was performed in order to Solution, microstructure modification, and reduce the residual stresses caused by selective laser melting process, further more aging was carried out in order to form copper-rich precipitates to strengthen the martensitic matrix. The microstructural studies after heat treatment showed columnar δ ferrite. Also the chromium and niobium carbides near the grain boundary were detected. Phase detection of different samples after heat treatment under different cycles showed different compositions of martensite and austenite. The Compression test results showed 49% increase in strength of 17-4PH steel made by selective laser melting method, under solution annealing heat treatment at 1050°C for one hour, followed by quench in water and after that aging at 480°C for one hour. Also, the micro hardness test showed 37% increase in hardness results after this cycle. The results of the potentiodynamic polarization test in the 3.5% sodium chloride solution indicated that the as-built sample had a better corrosion behavior than annealing and ageing samples.

ابوذر طاهري زاده , علي مالكي

محسن بدرسماي

بهزاد نيرومند , علي شفيعي