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Effects of ageing heat treatment temperature on the properties of DMLS additive manufactured 17-4PH steel

Świetlicki Aleksander, Wlaczak Mariusz, Szala Mirosław, Turek Marcin, Chocyk Dariusz

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 4

art. no. e146237

EN

Additive manufacturing (AM) is a modern, innovative manufacturing method that enables the production of fully dense products with high mechanical properties and complex shapes that are often impossible to obtain by traditional methods. The 17-4PH grade steel is often applied where high mechanical performance is required. 17-4PH, or AISI 630, is intended for precipitation hardening, an operation that combines solution and ageing treatments and is used to significantly change the microstructure of the steel and enhance its mechanical properties. This study investigates the effect of precipitation hardening on the properties of 17-4PH steel. To examine microstructure and morphology, metallographic tests were performed together with phase composition and chemical composition analyses. Mechanical parameters were determined via Vickers hardness testing and the Oliver-Pharr method. Samples were fabricated using direct metal laser sintering (DMLS), which is one of the powder bed fusion methods. The use of a constant solution treatment temperature of 1040_C and different ageing temperatures made it possible to evaluate the effects of ageing temperature on the mechanical properties and microstructure of 17-4PH. The presence of face-centered cubic FCC g-austenite and body-centerd cubic BCC a-martensite structures were detected. The tests revealed that – similarly to the wrought material – the highest hardness of 382_10:3 HV0:2 was obtained after ageing at 450_C. The nanoindentation test showed the same H/E ratio for the sample after fabrication and after solution treatment at 0.016769, but this value increased after ageing to 127–157.5%. The sample aged at 450_C was characterized by the highest H/E ratio of 0.026367, which indicates the highest wear resistance of this material under employed treatment conditions. In general, the sample treated at 450_C showed the best performance out of all tested samples, proving to have the smallest grain size as well as high Vickers and nanoindentation hardness. On the other hand, the use of solution treatment led to reduced hardness and improved workability of the AM material.

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Effect of shot peening on the surface properties, corrosion and wear performance of 17-4PH steel produced by DMLS additive manufacturing

Walczak Mariusz, Szala Mirosław

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

368--387

EN

Components produced by additive manufacturing (AM) via direct metal laser sintering (DMLS) have typical as-fabricated surface defects. As a result, surface properties of AM products should be modified to increase their strength, anti-wear behaviour, and at the same time to ensure their high corrosion resistance. Surface modification via shot peening is considered suitable for additive manufacturing of medical devices made of 17-4PH stainless steel. The objective of this study was to determine the effect of shot peening pressures (0.3 MPa and 0.6 MPa) and three types of blasting media (CrNi steel shot, nutshell granules and ceramic beads) on the tribological characteristics and corrosion resistance of specimens of DMLS 17-4PH stainless steel. Results demonstrated that shot peening caused steel microstructure refinement and-except for the nutshell shot-peened specimens-induced both martensite (α) formation and retained austenite (γ) reduction. 17-4PH specimens peened with steel and ceramic shots showed the highest increase in surface hardening by approx. ~ 119% (from 247 to 542 HV), which significantly improved their wear resistance. The highest mechanical properties (hardness and wear resistance) and corrosion resistance were obtained for the surfaces modified using the following media: ceramic beads > CrNi steel shot > nutshell granules. Adhesive and fatigue wear were two predominant mechanisms of tribological deterioration. Results demonstrated that the application of shot peening using ceramic beads led to grain size refinement from 22.0 to 14.6 nm and surface roughness reduction, which in turn resulted in higher corrosion resistance of the material. DMLS 17-4PH specimens modified by shot peening using ceramic beads and a pressure of 0.6 MPa exhibited the optimum surface morphology, hardness and microstructure, and thus improved wear and corrosion performance.

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Microstructure characterization of welds in X5CrNiCuNb16-4 steel in overaged condition

Ziewiec A., Zielińska-Lipiec A., Kowalska J., Ziewiec K.

Advances in Materials Science

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2019

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Vol. 19, nr 1(59)

57--69

EN

The paper presents the results of the investigation of microstructure of the welded X5CrNiCuNb16-4 (17-4PH) steel after solution treatment and aging at 620°C for different periods. The microstructure and the phase composition of the steel was investigated using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM) and the X-ray diffraction (XRD). Hardness was measured for samples aged at different times. Density distributions of Cu precipitates were established. The investigation has shown that the microstructure of the X5CrNiCuNb16-4 steel welds after aging at 620 ° C consists of tempered martensite, fine Cu precipitates and austenite. It was observed that the size of the Cu precipitates increases with increasing the aging time, what affects the decrease of hardness. Simultaneously, the quantity of reversed austenite increases with increase of aging time. It was revealed that enrichment of the austenite in Ni, Cu and C affects the increase of Ms, but this factor does not determine the stability of austenite.

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Odporność korozyjna spiekanych stali 17-4 PH o różnej porowatości po procesie azotowania w niskotemperaturowej plazmie

Brojanowska A., Załuska B., Kazior J., Wierzchoń T.

Ochrona przed Korozją

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2014

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nr 5

160--167

PL

Spiekane stale 17-4 PH (X5CrNiCuNb16-4) są coraz szerzej stosowane w różnych gałęziach przemysłu. Charakteryzują się one jednak m.in. niższą odpornością korozyjną i gorszymi właściwościami mechanicznymi w stosunku do stali litej, stąd też poddaje się je różnym obróbkom powierzchniowym, mającym na celu poprawę tych właściwości. W artykule omówiono wyniki badań struktury, składu fazowego i morfologii dyfuzyjnych warstw powierzchniowych na spiekanej stali 17-4 PH o dwóch stopniach porowatości po procesie azotowania jarzeniowego. Określono wpływ wytwarzanych warstw na odporność korozyjną w roztworze 0,5 M NaCl, badaną metodą bezprądową (rejestracja potencjału korozyjnego w czasie) i stałoprądową (krzywe polaryzacji). Wykazano, że dyfuzyjne warstwy azotowane zwiększają odporność korozyjną spiekanych stali 17-4 PH bez względu na stopień ich porowatości.

EN

Sintered 17-4 PH (X5CrNiCuNb16-4) steels are finding increasingly more applications in a variety of industries. However, one of their common features is lower corrosion resistance and inferior mechanical properties compared to solid steel, and for this reason, they often undergo varying surface treatment processes aimed at improving these properties. The article discusses the results of studies carried out on the structure, the phase composition and morphology of diffusion surface layers on sintered 17-4 PH steel of two degrees of porosity after glow-discharge nitriding. The electroless method (registration of corrosion potential over time) and the direct-current method (polarisation curves) were used to determine the impact of the developed layers on corrosion resistance. It has been shown that nitrided diffusion layers increase the corrosion resistance of sintered 17-4 PH steel, regardless of the degree of porosity.

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The effect of the addition of boron on the densification, microstructure and properties of sintered 17-4 PH stainless steel

Szewczyk-Nykiel A.

Czasopismo Techniczne. Mechanika

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2014

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R. 111, z. 2-M

85--96

EN

It is generally known that boron is an effective activator of the sintering process of iron as well as stainless steels. During sintering, boron contributes to the formation of a liquid phase wetting the surfaces of powder particles. As a consequence, a reduction of porosity, the rounding of pores and an increase in density is obtained. It is necessary to improve mechanical properties and corrosion resistance. The aim of this study is to investigate the effect of the addition of boron in the amounts of 0.2, 0.4 and 0.6% wt. on the density, microstructure and selected properties of sintered 17-4 PH stainless steel.

PL

Bor jest skutecznym aktywatorem procesu spiekania żelaza, ale także stali nierdzewnych. Podczas spiekania bor aktywuje proces spiekania w wyniku pojawienia się cieczy zwilżającej powierzchnie cząstek proszków. W konsekwencji przyczynia się do zmniejszenia porowatości, zaokrąglenia porów i wzrostu gęstości niezbędnego do poprawy właściwości mechanicznych i odporności na korozję. Celem przeprowadzonych badań było wyjaśnienie wpływu dodatku boru w ilości 0,2, 0,4 i 0,6 % ciężaru w postaci elementarnego proszku na kształtowanie się mikrostruktury i właściwości utwardzanych wydzieleniowo stali nierdzewnych gatunku 17-4 PH.

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Microstructure of Welded Joints of X5CrNiCuNb16-4 (17-4 PH) Martensitic Stainlees Steel After Heat Treatment

Ziewiec A., Zielińska-Lipiec A., Tasak E.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 3

965--970

EN

The paper presents rezults of microstructure (LM, TEM) investigation and hardness measurments of welded joints in martensitic precipitation hardened stainless steel containing copper, subjected to heat treatment. For the aging temperature up to 540°C even for the very long times, the microstructure of the welded joints is similar to this one at lower temerature aging. After aging at 620°C a distinct change of the microstructure was observed. Non-equilibrium solidification conditions of the weld metal, segregation and the diffusion of copper and the elements stablilizing the austenite cause the occurrence of the reverse transformation of the martensite into austenite as fast as just 1 hour at 620°C. TEM investigations revealed the differences in dispersion of hardening copper precipitates after aging at temperature 620°C for 1 and 4 hours.

PL

W artykule przedstawiono wyniki badań mikrostruktury (LM, TEM) oraz twardości złącz spawanych stali nierdzewnej martenzytycznej utwardzanej wydzieleniowo miedzią po obróbce cieplnej. Aż do temperatury starzenia 540° C mikrostruktura spoin nie wykazuje istotnych różnic niezależnie od czasu wytrzymania w porównaniu do tej obserwowanej w niższych temperaturach. Po starzeniu w temperaturze 620°C zaobserwowano wyraźne różnice w mikrostrukturze spoin. Nierównowagowe warunki krzepnięcia metalu spoiny, występowanie segregacji oraz procesy dyfuzji miedzi i pierwiastków stabilizujących austenit powodują wystąpienie przemiany odwrotnej martenzytu w austenit już po 1 godzinie starzenia w 620°C. Badania TEM wykazały, różnice w dyspersji cząstek umacniających w temperaturze starzenia 620°C przez 1 i 4 godziny.

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Mikrostruktura połączeń różnorodnych stali 17-4PH ze stopami niklu

Ziewiec A., Stępiński J., Tasak E.

Przegląd Spawalnictwa

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2013

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R. 85, nr 4

9--13

PL

Łączenie materiałów róźnorodnych ma duże znaczenie w przemyśle lotniczym i nuklearnym. Wykonano połączenia różnorodne Inconel 625– stal 17-4PH, Inconel 750 – stal 17-4PH metodą spawania plazmowego. Przeprowadzono badania mikrostruktury spoin za pomocą mikroskopu świetlnego i skaningowego, wykonano pomiary twardości w spoinie, strefie wpływu ciepła i materiale rodzimym. Badania wykazały, że metoda spawania plazmowego przy zastosowaniu odpowiednich parametrów spawania może być także stosowana przy otrzymywaniu połączeń różnorodnych stali 17-4PH ze stopami niklu.

EN

The joining of the dissimilar materials is very important in the aerospace and nuclear industry. The dissimilar joints of Inconel 625 – steel 17-4PH, Inconel 750 – steel 17-4PH were the plasma arc welded. The microstructure of the welds were studied using light microscopy and scanning electron microscopy. Hardness measurements of the weld, heat affected zone and base material were carried out. It was found that the plasma arc welding method using the suitable welding parameters may be also applied during the preparation of the dissimilar joints between 17-4PH steel and nickel alloys.