Effects of solid loading and cooling rate on the mechanical properties and corrosion behavior of powder injection molded 316 L stainless steel

    Effects of solid loading and cooling rate on the mechanical properties and corrosion behavior of powder injection molded 316 L stainless steel Muhammad Rafi Raza, Faiz Ahmad, Norhamidi Muhamad, Abu Bakar Sulong, M.A. Omar, Majid Niaz Akhtar, Muhammad Aslam PII: DOI: Reference:

S0032-5910(15)30206-0 doi: 10.1016/j.powtec.2015.11.063 PTEC 11384

To appear in:

Powder Technology

Received date: Revised date: Accepted date:

22 June 2015 23 November 2015 28 November 2015

Please cite this article as: Muhammad Rafi Raza, Faiz Ahmad, Norhamidi Muhamad, Abu Bakar Sulong, M.A. Omar, Majid Niaz Akhtar, Muhammad Aslam, Effects of solid loading and cooling rate on the mechanical properties and corrosion behavior of powder injection molded 316 L stainless steel, Powder Technology (2015), doi: 10.1016/j.powtec.2015.11.063

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EFFECTS OF SOLID LOADING AND COOLING RATE ON THE MECHANICAL PROPERTIES AND CORROSION BEHAVIOR OF POWDER INJECTION MOLDED 316 L STAINLESS STEEL

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Department of Mechanical and Materials Engineering, Universiti Kebangsaan Malaysia, Bangi, Selangor Malaysia Department of Mechanical Engineering, Universiti Teknologi PETRONAS, Malaysia 4-

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Muhammad Rafi Raza 1,2*, Faiz Ahmad 3, Norhamidi Muhamad 2, Abu Bakar Sulong2, M. A. Omar4, and Majid Niaz Akhtar1,5 , Muhammad Aslam3 1Department of Mechanical Engineering, COMSATS Institute of Information Technology,Sahiwal 57000 ,Pakistan

Advanced Materials Research Centre (AMREC) SIRIM, Malaysia

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5- Department of Physics, COMSATS Institute of Information Technology,Lahore Pakistan

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Abstract

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Solid loading and post-sintered cooling rates are two effective parameters used to control the mechanical properties of powder-injection molded parts. In the case of 316L stainless steel (SS), these parameters also influence mechanical properties and corrosion resistance. In this study, four formulations with

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powder loading above and below the critical powder loading were prepared and sintered at 1325 °C in vacuum with cooling rates varying from 3 °C/min to 10 °C/min. Solid loadings above the critical loading caused reductions in final properties (i.e. mechanical properties and corrosion resistance) because of increased porosity. The high cooling rate of 10 °C/min improved the mechanical properties due to the formation of large number of grains and corrosion resistance due to formation of chromium oxide layer at the surface of PIM 316L SS. Solid loading of 65 vol.% , sintered at 1325 °C with cooling rate of 10 °C/min showed improvements in terms of mechanical properties and corrosion resistance compared with conventional 316L SS. Such improvements were considered due to reduced grain sizes and formation of a chromium oxide layer on the sample surface. This study identify the solid loading 1

ACCEPTED MANUSCRIPT (65vol.%) below the critical powder loading and a high post-sintered cooling rate, i.e., 10 °C/min, are suitable to achieve optimum mechanical properties and corrosion resistance in 316L SS. The developed

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material may be recommended for biomedical applications.

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Keywords: powder-injection molding, solid loading, cooling rate, mechanical properties, morphology,

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corrosion behavior

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* Corresponding Author. Tel: +9240-4305666; Fax: +9240-4305006; e-mail: [email protected]

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1. Introduction

Powder injection molding (PIM) is an excellent technology that combines powder metallurgy and

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polymer-injection molding, suitable to produce complex parts with dimensional accuracy at

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comparatively low prices [1, 2]. The PIM process consists of four consecutive steps: mixing, molding, debinding, and sintering [3, 4]. In PIM, every step presents a unique importance that ultimately affects

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the final properties of the parts produced by PIM. Over the last few decades, researchers have studied the effects of various processing parameters, such as particle size and its distribution, binder [5], powder

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loading and rheology [6], powder binder separation [7, 8] , mold design and molding parameters [9] ,debinding [10, 11] and sintering parameters (i.e., modeling [7], atmosphere [12] , heating, and cooling rate [4] ) on the densification, foamabality and final mechanical properties of 316L SS. Tang et al. investigated the effects of palladium coatings on the corrosion resistance of 316L SS in acidic environments and found that these coatings improved corrosion resistance in non hydrogen [13]. Sobral et al. tested PIM 316L SS in salt environments and found that the presence of porosity initiates corrosion [14]. Rafi et al. [4] studied role of cooling rate on corrosion resistance of 316L SS and found that higher post sintered cooling rate is responsible to improve the corrosion resistance. García et al. also studied the effects of sintering atmosphere on the corrosion resistance of 316L SS produced by powder metallurgy and concluded that vacuum sintering helps attain high density and better corrosion resistance 2

ACCEPTED MANUSCRIPT compared with gas sintering [15, 16]. Li and Bell investigated the corrosion properties of AISI 316 austenitic stainless steel (SS) treated through active screen plasma nitriding (ASPN); these researchers

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tested corrosion through weight loss in acid and salt environments and found that ASPN at low

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temperatures, i.e., 450 °C, improves the corrosion resistance of steel by forming a nitride layer on the

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sample surface [17].

Corrosion is the major cause of failure of metallic implants while implanted in the human body [18].

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Several factors, including alloy composition, fabrication method, and environment, affect the corrosion rate of the implants. A lot of metals and their alloys are used in the medical industry as medical

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implants. Among commonly utilized metals, 316L SS implants are recommended because of their low cost, excellent combination of mechanical properties and corrosion resistance, availability, and easy

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fabrication compared with other alloys. However, 316L SS implants release metal toxic ions, such as Fe,

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Ni, and Cr, which leads to allergies and carcinogens [19]. A review of retrieved implants shows that

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90% of all reported failures is attributed to corrosion [20]. The objective of the present study is to study the effects of powder loading and post-sintered cooling rate on the mechanical properties and corrosion resistance of PIM 316L SS. The molded test samples are

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debonded and sintered in a vacuum atmosphere. The sintered test samples were characterized in terms of densification, tensile-strength measurements, morphology, measurement of toxic metal ions, and corrosion resistance according to ASTM standards.

2. Experimental Materials and Methods 2.1. Materials and Injection Molding PACIFIC SOWA, Japan, supplied the commercial water-atomized SS 316L (PF-10R) with tap density 4.55g/cm3 and theoretical density 7.92g/cm3. The relevant particle sizes are given in Table 1, and the

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ACCEPTED MANUSCRIPT chemical composition of the powder provided by the supplier according to ASTM standard F138-08 is

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shown in Table 2.

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Table 1: Measured particles size distribution of 316L SS

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Table 2: Chemical composition of 316L SS (PF-10R) according to ASTM standard F138-08 The critical solid loading was measured by using torque rheometry. During the experiment, oleic

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acid was used as a binder. At critical powder loading, the metal particles are tightly packed without external pressure, and the voids between particles are completely filled with the binder. The critical solid

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loading can help determine the optimum solid loading.

After determination of the critical powder loading (i.e. 66vol%) , four formulations of feedstock, i.e., F1,

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F2, F3, and F4, above and below the critical solid loading were prepared with solid loadings of 60

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vol.%, 65 vol.%, 67 vol.%, and 69 vol.%, respectively. Multi component binder system was used and

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consist of Paraffin Wax (PW) 75 vol.% , Polypropylene (PP) 20 vol.% and Stearic Acid (SA) 5 vol.%. SS powder and wax-based binder were mixed using a Z-blade mixer at 180 ±5 °C for 90 min at 60 rpm. After mixing, the paste was dried and converted into granules. The test specimens were molded using a

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100 KSA vertical injection molding machine according to MPIF standard 50. All formulations were molded at 180 °C. The molding dwell time was varied from 18–30 s depending on the solid loading. No physical defects were observed on the surface of the test samples. 2.2. Debinding and Sintering Removal of the polymer binder from the molded samples is known as debinding and process was completed through two consecutive steps involving solvent extraction followed by thermal debinding [4]. Solvent extraction was performed by using a water-circulating bath and test samples were immersed for 5 h at 60 °C to extract the paraffin wax (major binder component). Thermal-debinding was performed at 450 °C for 1 h at a heating rate of 7 °C/ min to remove the remaining binder (PP and SA ) 4

ACCEPTED MANUSCRIPT . Debonded test samples were sintered in a vacuum (graphite heating element furnace) at 1325 °C with a dwell time of 2 h and post sintering cooling rates of 3, 5, or 10 °C/min to investigate the effects of post-

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sintered cooling rate on the densification, mechanical properties, and corrosion resistance of the PIM

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316L SS test samples. 2.3. Characterization of Sintered Samples

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The density of sintered test samples was measured using the water immersion technique, and tensile strengths were determined using an Amsler 100 (Zwick/Roell) system according to ASTM standard

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methods ASTM B0311-93R02E01 and E8M-00 respectively. The carbon content in the sintered test samples was determined according to ASTM standard E1019. The morphological and elemental analysis

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results of sintered test samples at different cooling rates were evaluated. Samples selected from each

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formulation batch were analyzed through FESEM and EDX after 30 d of immersion in Ringer’s solution (i.e. simulated body solution). Test samples for corrosion measurement were prepared according to

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ASTM standard G-01. Weight loss tests were performed to study the corrosion behavior of the sintered test samples. Test specimens were immersed in Ringer’s solution, at 37 ± 1 °C for 30 d. The pH of the

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solution was maintained at 7.4 using 1 M solutions of HNO3 and NaOH. After completion of the weight loss test, the solutions were analyzed for metal ion concentrations through atomic absorption spectroscopy.

3. Results and Discussion 3.1. Critical Loading by Torque Rheometry The critical solid loading was measured through torque rheometry using a Brabender instrument according to ASTM standard D-281-31. The torque behavior of 316L SS is shown in Figure 1. Oleic acid was initially added to the binder with stainless-steel powder, after which the torque became 5

ACCEPTED MANUSCRIPT unstable. This result is attributed to the non-homogeneous mixture of the powder and oleic acid. When the torque had become stable, which was attributed to the homogeneous mixture, the torque value was

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noted. Further addition of oleic acid increased the torque, which means voids between the oleic acid and

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powder were filled and the torque value increased. The maximum torque was noted when the amount of

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oleic acid was 13 ml; at this stage, metal particles are completely coated with the binder without any external pressure and that all of the voids between the particles are filled with the binder with further

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additions of oleic acid. Finally, the torque value began to decrease. This result may be attributed to variations in oleic acid in the mix or the shear effect from the increased amount of mass in the

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compounder. The calculated solid loading volume in this study was 66 vol.%; this value is also known as the critical solid loading which is in the range accepted globally for 316L stainless steel with particle

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size 5µm [21]. At the critical solid loading, the feedstock has low viscosity and good particle-to-particle

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contact. optimum solid loading is up to 5% less than the critical powder loading where excess binder

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provided an easy flow of the feedstock in mold cavity [3]. Considering the experimental results, the optimum solid loading was within the range of 61 vol.% to 66 vol.%.

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Figure 1: Torque scan for the critical solid loading of 316L SS powder with addition of oleic acid

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ACCEPTED MANUSCRIPT 3.2. Effects of Solid Loading and Cooling Rate on Sintered Density

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Figure 2 demonstrates that F1 features a 1.8% increment in sintered density when the post-sintering

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cooling rate is increased from 3 °C/min to 10 °C/min but in case of F2 this increment was 2%. This may

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be due to large number of grains and higher post sintering cooling rate (Hall-Petch effect). Sintered density of F3 and F4 was decreased as compared to F1 and F2 on increasing the post-sintering cooling rate from 3 °C/min to 10 °C/min. This result may be attributed to powder loadings above the critical

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loading.

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Experimental results revealed that the post-sintering cooling rate is also an efficient factor to achieve maximum sintered density. Rapid post-sintering cooling rates reduce the nucleation growth time and result in reductions in grain size, which improve the sintered density [22]. The sintered density achieved

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in this study was comparable with the ASTM standard for wrought SS [23].

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Figure 2: Effects of Solid loading and post sintering cooling rate on sintered density at 1325˚C 3.3 Effects of Solid Loading and Cooling Rate on Tensile Strength of Sintered Parts

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Figure 3 shows the tensile strengths of vacuum-sintered test samples. Among the test samples cooled at 10 °C/min, F2 showed a tensile strength of 502 MPa, and the strength achieved by this sample was 4.3% higher than that achieved by F1. The increment in strength in F3 was 2.3 %, and the tensile strength of F4 was equal to that of F1 i.e. 480MPa. On the basis of these results, this study can concludes that higher cooling rates are suitable for obtaining an excellent combination of tensile strength and ductility [24]. From the tensile results obtained, it can be concluded that higher post-sintered cooling rate is responsible for increasing the tensile strength of the samples. This improvement may be attributed to smaller grain size. Reduction in tensile strength occurred when the solid-loading value exceeded the critical solid loading. The presence of dimples during the fracture shows that the test samples are ductile 7

ACCEPTED MANUSCRIPT in nature as shown in Figure 4. A good combination of tensile strength and elongation behavior was achieved for the test samples sintered at 1325 °C with a post-sintering cooling rate of 10 °C/min and are

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comparable with that of wrought 316L SS (according to ASTM standards) [23].

1325˚C

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Figure 3: Effects of solid loading (vol. %) and cooling rate on tensile strength of vacuum sintering at

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Figure 4: Fracture of vacuum sintered test sample showing dimples, evidence of ductile nature

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3.4 Effects of Cooling rate on Morphology of Sintered parts A considerable difference in porosity of sintered samples was noted for the test samples of F1 and

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F2 sintered at 1325˚C and post sintered cooling rate 5˚C/min and 10˚C/min. Figure 5-a and 5-b

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show a visible decrease in porosity for the test sample sintered at 1325˚C and post sintered cooling rate 5˚C/min and 10˚C/min. The pores were irregular in shape and distributed across the grain

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boundaries as well as within the matrix as shown in Figure 5-a. The number of pores further decreased and their sizes became relatively small when the post-sintering cooling rate was increased

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to 10 °C/min as shown in Figure 6. Both formulations that had a cooling rate of 10 °C/min showed less porosity compared with those with a cooling rate of 5 °C/min, clear in Figure 5 and 6. At this temperature, the pores were irregular in shape. A large number of grains with small size were grew well under a cooling rate of 10 °C/min, which caused to reduce steel porosity [22]. Grain size influenced the mechanical properties of the samples, and differences in grain growth and reductions in porosity are clear in Figure 6. Figure 5 : SEM micrograph of the test sample (F1 ) sintered at 1325˚C showing reduction in porosity; (a) 5˚C/min, and (b) 10˚C/min

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ACCEPTED MANUSCRIPT Figure 6 : FESEM micrograph of test sample (F2) showing the variation in porosity at cooling rate of ;

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(a) 5˚C/min, (b) 10˚C/min

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The FESEM micrograph in Figure 6 reveals that an increase in post-sintering cooling rate reduces

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porosity, helps to isolate the pores from each other, and move them away from grain boundaries thus grain boundaries became more prominent. Figure 7 shows the EDX analysis results of the test samples sintered at 1325 °C with a post-sintering cooling rate of 10 °C/min. Three elements, Fe, Ni, and Cr, were

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detected during EDX analysis. The amount of Cr observed was 15.57 %, which means that Cr was

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retained within the matrix. Higher post sintered cooling rate reduced the diffusion time to Cr and as a result formation of carbide was minimized. No evidence supported the presence of carbide in the samples as confirmed from XRD results shown in Figure 8. The XRD results showed the austenitic

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structure according to JCPDS card no 00-033-0397.

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Figure 7: Micrograph and EDX of F2 with cooling rate of 10˚C/min shows no evidence of carbon Figure 8: XRD pattern of vacuum sintered samples showing austenitic structure without carbides

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Small white-colored particles were observed on the surface of the sintered steel, and the number of particles increased as the post-sintered cooling rate increased, as shown in Figures 9-11. Test samples obtained with higher post-sintering cooling rates showed a uniform amorphous film of Cr oxide on their surface, as shown in Figure 11, and higher resistance for corrosion compared with samples obtained with low post-sintering cooling rates. At a high cooling rate, the oxide layer was amorphous in nature and white in clour, as shown in Figure 11. This white-colored layer was identified as a combination of Cr and O2. EDX analysis of these layers showed that the amount of oxygen measured was as high as 48 % when the post-sintering cooling rate was 10 °C/min, as shown in Figure 12. The presence of more Cr on the surface of the samples formed an enriched Cr oxide layer, which protects the samples from the chloride environment. Previous research demonstrated the same morphology of oxide film on 316L SS [13].

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ACCEPTED MANUSCRIPT Figure 9: Morphology shows the distribution of the oxide particles at the surface of vacuum sintered

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(F2) with the cooling rate of 3˚C/min

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Figure 10: Morphology of the corroded sample (F2) with post sintered cooling rate of 5˚C/min

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Figure 11: Morphology of the corroded PIM 316L (F2) samples sintered with post sintering cooling rate of 10˚C/min

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Figure 12: EDX analysis of corroded samples sintered cooling rate of 10˚C/min showing presence of O2

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(a) morphology (b) EDX (c) morphology (d) EDX 3.5. Effects of Cooling Rate on Corrosion Behavior of PIM 316L SS

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The corrosion behavior of vacuum-sintered test samples at 1325 °C is shown in Figure 13. Among the

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formulations studied, F2 showed a low corrosion rate of 0.17 mpy when the test samples were cooled at 10 °C/min. Further increases in solid loading beyond the critical solid limit reduced corrosion resistance.

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Higher corrosion resistance was attributed to the reduced porosity achieved in formulation F2 at a high post-sintering cooling rate, as shown in Figure 2. High post-sintering cooling rates helped minimize

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carbide formation, as shown in the FESEM micrograph and EDX analysis results in Figure 7. High vacuum-sintering environments retained the maximum amount of Cr, which helps form an enriched Cr oxide layer on the surface of the test samples. This layer can protect the steel from corrosion environment in human body. Based on the results shown in Figure 13, it is concluded that the corrosion rate decreases by increasing the solid loading below the critical solid loading, i.e., 66 vol.%. This result was attributed to the decrease of pinhole porosity of the sintered samples. High-vacuum sintering and higher post sintering cooling rate used in this study minimize Cr evaporation during sintering and enhance the formation of Cr3O2 passive layer during cooling respectively. This approach resulted in the retention of Cr on the surface of the test sample in the form of a passive oxide layer (Cr3O2), which improves corrosion resistance .Higher post10

ACCEPTED MANUSCRIPT sintering cooling rate provided less diffusion time to the Cr within the matrix and inhibit carbide formation [25-28]. The results achieved are better than those previously reported for 316L SS tested in a

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chloride environment [29].

Figure 13: Corrosion rate of the vacuum sintered samples at 1325˚C with different post sintering cooling

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Detailed atomic absorption spectra are given in Table 3. A large number of metal ions were released

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from sintered samples with solid loadings above the critical loading and low post-sintered cooling rates. The trace analysis results obtained in Ringer’s solution after weight loss measurement are shown in

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Table 3. Significant amounts of Ni, Cr, and Fe ions were detected in the solutions of gas-sintered

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samples. The release of these ions depends on several factors, such as porosity and formation of oxide layers on the surface of the sample. Table 3 shows that the release of metal ions (i.e., Fe. Ni, and Cr

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ions) decreases for the samples cooled at higher post-sintered cooling rate an this is considered due to decreases in porosity. This result may also be attributed the slow evaporation of Cr atoms during high

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vacuum-sintering and post-sintering cooling. The Cr atoms settle on the surface of the steel and its diffusion is slower as compared to Fe and Ni. Thus, most of the Cr is retained on the surface of the steel during high cooling rate and forms a passive oxide layer. This layer protects the steel against corrosion and minimize the release of metal ions. We thus conclude that the amount of metal ions was well below toxic limits and not harmful to human tissues [19, 30-32]. Table 3: Release of the metal ions from vacuum sintered samples in Ringer’s solution after the corrosion test

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ACCEPTED MANUSCRIPT 4. Conclusion

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In the present study, development of 316L SS with improved mechanical properties, low porosity,

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enhanced corrosion resistance, and minimal release of toxic metal ions was achieved through PIM. With

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this particle-size distribution, critical solid loading was identified at 66 vol.%. Solid loading and sintering parameters played an important role in controlling the mechanical properties and corrosion resistance of 316L SS. F2 samples sintered in a vacuum at 1325 °C with a post-sintering cooling rate of

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10 °C/min showed a tensile strength of 501 MPa, a hardness of 204 Hv, a sintered density of 96%, and a

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corrosion resistance of 0.17 mpy. The results obtained, solid loadings below the critical loading (i.e., 65 vol.%) and a rapid post-sintering cooling rate, i.e., 10 °C/min during vacuum sintering at 1325 °C resulted in improved mechanical properties and no carbide formation across grain boundaries, which is

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helpful in producing a chromium oxide passive layer at the surface of the sintered samples. Formation of this layer improves the corrosion resistance of the steel and minimizes of the release of toxic metal ions.

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. Leaching of toxic-metal ions, including Ni (0.0001 ppm), Cr (0.0006 ppm), and Fe (0.0036ppm), was far below limits considered toxic to humans. Thus, the method proposed in this work may be

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recommended for medical applications.

Acknowledgements

The authors wish to thank Universiti Teknologi PETRONAS, Advanced Materials Research Centre (AMREC) SIRIM, Kulim, Malaysia, and Universiti Kebangsaan Malaysia for providing the laboratory facilities and financial support.

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modification of biometallic materials, J Mater Sci: Mater Med, 8 (2007) 725-751.

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ACCEPTED MANUSCRIPT EFFECTS OF SOLID LOADING AND COOLING RATE ON THE MECHANICAL PROPERTIES AND CORROSION BEHAVIOR OF POWDER INJECTION MOLDED 316 L STAINLESS STEEL

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Figure 1: Torque scan for the critical solid loading of 316L SS powder with addition of oleic acid

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Figure 2: Effects of Solid loading and post sintering cooling rate on sintered density at 1325˚C

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Figure 3: Effects of solid loading (vol. %) and cooling rate on tensile strength of vacuum sintering at 1325˚C

Figure 4: Fracture of vacuum sintered test sample showing dimples, evidence of ductile nature

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Figure 5 : SEM micrograph of the test sample (F1 ) sintered at 1325˚C showing reduction in porosity;

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(a) 5˚C/min, and (b) 10˚C/min

Figure 6 : FESEM micrograph of test sample (F2) showing the variation in porosity at cooling rate of ; (a) 5˚C/min, (b) 10˚C/min

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Figure 7: Micrograph and EDX of F2 with cooling rate of 10˚C/min shows no evidence of carbon Figure 8: XRD pattern of vacuum sintered samples showing austenitic structure without carbides

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Figure 9: Morphology shows the distribution of the oxide particles at the surface of vacuum sintered (F2) with the cooling rate of 3˚C/min

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Figure 10: Morphology of the corroded sample (F2) with post sintered cooling rate of 5˚C/min Figure 11: Morphology of the corroded PIM 316L (F2) samples sintered with post sintering cooling rate of 10˚C/min

Figure 12: EDX analysis of corroded samples sintered cooling rate of 10˚C/min showing presence of O2 (a) morphology (b) EDX Figure 13: Corrosion rate of the vacuum sintered samples at 1325˚C with different post sintering cooling rates

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Figure 1:

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Figure 2:

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Figure 4 :

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Figure 3:

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(b)

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(a)

(b)

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Figure 6:

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Figure 7:

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Figure 8:

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Figure 10:

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Figure 9:

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Figure 11:

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Figure 12:

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Figure 13: 3˚C/min 5˚C/min 10˚C/min

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0.8

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0.6 0.4 0.2

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Corrosion Rate (mpy)

1.0

0.0 60

65 Solid loa ding(vol.%)

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70

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EFFECTS OF SOLID LOADING AND COOLING RATE ON THE MECHANICAL PROPERTIES AND CORROSION BEHAVIOR OF POWDER INJECTION MOLDED 316 L STAINLESS STEEL

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Table 1: Measured particles size distribution of 316L SS

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Table 2: Chemical composition of 316L SS (PF-10R) according to ASTM standard F138-08 Table 3: Release of the metal ions from vacuum sintered samples in Ringer’s solution after the corrosion

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Table 1: D90

1.43 4.42 7.63

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Particle size (µm)

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Table 2:

C

Si

Mn

P

Wt.%

0.024

0.36

0.07

0.029

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Element

S

Ni

Cr

Mo

Cu

0.002

10.53

16.57

2.1

0.1

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Table 3:

Ni

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3˚C/min

Formulation

F1

D50

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Particle Distribution D10

Cr

Fe

5˚C/min Ni

Cr

10˚C/min Fe

Ni

Cr

Fe

0.0011

0.0049

0.0008

0.0002

0.0046

0.0016

0.0004

0.0042

0.0006

0.0002

0.0008

0.0004

0.0001

0.0004

0.0001

0.0006

0.0036

0.001

0.0002

0.0014

0.0016

0.0004

0.0012

0.002

0.0006

0.004

0.002 * ppm unit for metal ions

0.0009

0.0018

0.001

0.0008

0.001

0.001

0.0014

0.0024

F3 F4

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0.0021

F2

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Graphical abstract

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Highlights Critical solid loading effects on densification and its role in biocompatibility

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Linkage between PIM process parameters and its effects on sintered properties of 316L stainless steel.

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Effects of post cooling rate on formation of biocompatible oxide layer (Cr3O2) and to avoid the carbide formation.

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Relationship between Sintering temperature and evolution of corresponding microstructures.

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