Comprehensive experimental study of shot peening on the surface integrity evolution of 12Cr2Ni4A high-strength steel

Abstract

Despite the broad study of surface integrity in shot peening, the evolution mechanism of surface morphology considering the initial processing feature is still unclear, which hinders the optimization of peened surface quality. In this study, two typical surfaces (grinding and polishing) were selected to be the initial surface morphology for shot peening. Then the effects of initial surface morphology on peened surface integrity were investigated, including 3D surface morphology, surface roughness, residual stress distribution, and microhardness. It could be found that the processing features of the initial surface still exist but are flattened, even at a relatively high coverage. The shot peening simulation also revealed this flattening effect. Besides, the effect of coverage on surface integrity was investigated. The 12Cr2Ni4A sample with 200% coverage has smaller surface roughness and similar residual stress distribution than 100% coverage, which is different from previous studies on medium-strength steels and lightweight alloys. These results provide a reference for understanding the surface integrity evolution in shot peening.

Appendix

The 3D parameters used in the present work were the following [73]:

S_q: root mean square height of the scale-limited surface;

$${S}_{\text{q}}=\sqrt{\frac{1}{A}\underset{A}{\iint }{z}^{2}\left(x,y\right){\text{d}}x{\text{d}}y}$$

(3)

S_sk: skewness of the scale-limited surface;

$${S}_{\text{sk}}=\frac{1}{{S}_{q}^{3}}\left[\frac{1}{A}\underset{A}{\iint }{z}^{3}\left(x,y\right){\text{d}}x{\text{d}}y\right]$$

(4)

S_ku: kurtosis of the scale-limited surface;

$${S}_{\text{ku}}=\frac{1}{{S}_{q}^{4}}\left[\frac{1}{A}\underset{A}{\iint }{z}^{4}\left(x,y\right){\text{d}}x{\text{d}}y\right]$$

(5)

S_p: maximum peak height of the scale limited surface;

$${S}_{\text{p}}=\mathrm{max}\left[z\left(x,y\right)\right]$$

(6)

S_v: maximum pit height of the scale limited surface;

$${S}_{\text{v}}=\left|\mathrm{min}\left[z\left(x,y\right)\right]\right|$$

(7)

S_z: maximum height of the scale-limited surface;

$${S}_{\text{z}}={S}_{\text{p}}+{S}_{\text{v}}$$

(8)

S_a: arithmetical mean height of the scale limited surface.

$${S}_{\text{a}}=\frac{1}{A}\underset{A}{\iint }\left|z\left(x,y\right)\right|{\text{d}}x{\text{d}}y$$

(9)

The 2D parameters used in the present work were the following [74]:

R_q: root mean square value of the assessed profile;

$${R}_{\text{q}}=\sqrt{\frac{1}{l}\underset{0}{\overset{l}{\int }}{Z}^{2}\left(x\right){\text{d}}x}$$

(10)

R_p: maximum profile peak height;

$${R}_{\text{p}}=\mathrm{max}\left[Z\left(x\right)\right]$$

(11)

R_v: maximum profile valley depth;

$${R}_{\text{v}}=\left|\mathrm{min}\left[Z\left(x\right)\right]\right|$$

(12)

R_z: maximum height of profile;

$${R}_{\text{z}}={R}_{\text{p}}+{R}_{\text{v}}$$

(13)

R_a: arithmetical mean value of the assessed profile.

$${R}_{\text{a}}=\frac{1}{l}\underset{0}{\overset{l}{\int }}\left|Z\left(x\right)\right|{\text{d}}x$$

(14)