Influence of Cryogenic Treatment and Shot Peening on Material Properties of CrMoV Low Alloy Steels

Abstract

Optimize Cryogenic Parameters: Standard deep cryogenic treatment (DCT) typically uses a single soak, but modifications can further refine the microstructure: Extend Soaking Time: Increasing soak duration (e.g., from 12 to 24 or 36 hours) at (77 K) can maximize the transformation of retained austenite to martensite and further promote the precipitation of fine eta-carbides.

Cyclic Cryogenic Treatment: Implementing multiple cooling and warming cycles (e.g., 2–3 cycles) instead of one can lead to even finer carbide distribution and improved impact strength (up to 17% increase) compared to single-cycle treatments.

Refine Shot Peening Strategy: Moving from conventional to advance peening techniques can significantly improve the surface stress profile: Double Peening: Apply a primary high-intensity shot (e.g., S170 or S230) to create deep compressive residual stresses, followed by a secondary peening with smaller, finer media (e.g., glass beads or S110). This reduces the surface roughness caused by the first stage while maintaining or even increasing the peak compressive stress.

Severe Shot Peening (SSP): Increasing the coverage (e.g., to 200% or higher) and using higher Almen intensities can induce a nanostructured surface layer. This provides superior surface hardening (up to 330 HV) and significantly better fatigue resistance than conventional methods.