Macroscopic and microscopic evolutions of a shot-peened layer during isothermal recovery

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 31; no. 1; pp. 213 - 224
• Main Authors: LILLAMAND, I, BARRALLIER, L, SPRAUEL, J. M, CHIRON, R
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 2000; Springer Nature B.V
• Subjects: Applied sciences; CHROMIUM-MOLYBDENUM STEELS; Exact sciences and technology; MATERIALS SCIENCE; Metals. Metallurgy; MICROSTRUCTURE; Polishing. Blast cleaning; Production techniques; RESIDUAL STRESSES; SHOT PEENING; STRAIN HARDENING; Surface treatment; Stress analysis; Theoretical study; Shot peening; Steel; Hardness; Experimental study; X ray diffraction; Recovery; Surface treatment; Dilatometry; Mechanical treatment; Depth profile; Residual stress
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-000-0066-6

The present study deals with the recovery of work-hardened layers, which are often encountered in mechanical parts. Two simple cases are studied for the 38Cr4Mo steel: the shot-peened layer of semi-infinite bodies and a ground surface. The latter case is applied to in situ tensile samples using the gold microgrids technique developed at PMTM Laboratory in order to determine some possible dimensional changes. Both work-hardened layers show the existence of macroscopic straining during the recovery. For the only shot-peened layer, a phenomenological study provides the evolution of the residual stresses and the integral breadth depth profiles using x-ray difractometry. A method is proposed to determine the recovery strain field from the residual stresses evolution. As the only possible strain on a semi-infinite body lies along the normal axis to the surface, calculated recovery strains are compared with the dimensional measurements. On the microstructural viewpoint, the modified Warren-Averbach's analysis is quickly presented and is performed to analyze the x-ray peak broadening through the affected layer of a shot-peened sample. Several corrections and deconvolution calculations of the x-ray profiles finally lead to the second and third types of broadening effects and their microstructural interpretations.