PSI - Issue 14

Manojakumar Chimmat et al. / Procedia Structural Integrity 14 (2019) 746–757 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

748

3

optimized to ensure dense samples (> 99.95% density). Two sets of samples were built for each geometry for measurements in the as printed and heat treated condition. Grit blasting was carried out on the as printed Cube and Coupon surfaces, using glass beads, at 7.5 bar pressure, for 5 mins, at an angle of 45 degrees in order to study the residual stresses on the surface after grit blasting CoCrMo was heat treated at three different temperatures, 950°C, 1050°C and 1150°C, in vacuum for 4 hours, in order to study the microstructural response and residual stress to heat treatment, to examine its suitability for high temperature applications. SS316L alloy was subjected to a stress relieving heat treatment at 650°C for 2 hours 30 minutes, in air.

Longitudinal

b

a

Top

YZ

Tra nsv ers e

L o n gi tu di n al

2 1

4 3

Side A

XZ

Transverse

Fig. 1. Schematic of the (a) as printed Cube (b) flat plate (Coupon) (FRARENDI 2018)

Table 1. Nominal chemistry of the alloys in weight %

Alloy

C

Cr

Mo

Ni

Si

Mn

P

S

Fe

Co

SS316L

0.03

18

3

14

0.75

2

0.045

0.03

62.14

-

CoCrMo

0.1

28.7

7

-

0.9

0.9

-

-

-

62.4

The powders were analyzed using a particle size analyzer, Mastersizer 2000E, a laser diffraction-based powder size analyzer. SEM-EDS analysis was performed on Zeiss EVO18 Scanning Electron Microscope (SEM) along with Oxford link energy dispersive spectroscopy (EDS) to characterize the morphology and composition of the powders. Surface roughness was measured on the as printed and grit blasted samples using a Zeiss Surfcom 1800D surface profilometer having a trace length of 4 mm, cut off wavelength 0.8 mm and traverse speed of 0.030 mm/sec.

Table 2 Process parameters of CoCrMo

Parameters

CoCrMo

SS316L

Laser power (W)

290

200

Laser beam diameter (µm) Scanning Speed (mm/sec)

80

80

950 0.11

825 0.11

Hatch distance (mm) Layer thickness (µm)

40

20

Table 3. Parameters for X-ray residual stress measurements CoCrMo (SS316L)

Counting time (Sec)

100

2θ (degrees)

130 (128.1)

ψ angles (degrees)

0,5,10,15,20,25,30,35,40,45,50,55,60

Stress constant (MPa/deg) Young’s modulus (GPa)

-754.39 (-663.57)

235 (200) 0.3 (0.28)

Poisson’s ratio