TEM analysis was performed in this study to analyze microstructural changes of a quenched and tempered 39NiCrMo3 low alloy steel as a function of the kinetic energy induced by means of different shot peening treatments: conventional (CSP) and severe (SSP). Residual stresses and microhardness evolution in depth were also determined by means of an X-ray diffractometer and microhardness tester, respectively. Surface roughness depending on the applied shot peening treatment was also analyzed.

TEM analysis reveals that plastic deformation induced by the CSP treatment promotes ferrite amorphization and the reduction of carbides grain size to nanometric scale. On the other hand, after applying SSP treatments, (Fe,Cr)₂₃C₆ nanocrystals are nucleated from the amorphous matrix previously created. Accordingly, the amorphous matrix obtained in the earliest stages of the SP treatment seems to contribute to promote new nanostructures at the end of the SSP.

Regarding the mechanical features evolution, the maximum compression stress value was similar in all the shot peening treatments, in the range of −450 MPa, while the thickness of the affected layer by the compressive residual stresses increased when SSP treatments were applied. Microhardness measurements evidenced a notable hardening in the upper layer of the material, increasing with the coverage level. The thickness of the affected layer in depth was around 200 μm, for all the series. The influence of the CSP and the SSP on the steel hardening was also corroborated by FWHM (Full Width at Half Maximum) measurements.

在这项研究中进行了TEM分析，以分析淬火和回火的39NiCrMo3低合金钢的微观结构变化，该变化是通过不同的喷丸处理方法（常规（CSP）和严重喷丸处理）所诱发的动能的函数。还分别通过X射线衍射仪和显微硬度计测定残余应力和显微硬度。还分析了取决于所应用喷丸处理的表面粗糙度。

TEM分析表明，CSP处理引起的塑性变形促进了铁素体的非晶化，并使碳化物的晶粒尺寸减小至纳米级。另一方面，在进行SSP处理后，（Fe，Cr）₂₃ C ₆纳米晶体从先前形成的非晶基质中成核。因此，在SP处理的早期阶段获得的无定形基质似乎有助于在SSP结束时促进新的纳米结构。

关于机械特征的演变，在所有喷丸处理中，最大压缩应力值在-450 MPa范围内相似，而当采用SSP处理时，受压缩残余应力影响的层的厚度会增加。显微硬度测量表明，材料的上层有明显的硬化，随覆盖率的增加而增加。对于所有系列，受影响层的深度深度约为200μm。CW和SSP对钢硬化的影响也通过FWHM（半高全宽）测量得到了证实。