What process is commonly used to harden cylinder barrels?

Nitriding is a heat treatment process that introduces nitrogen into the surface layer of steel, creating a hard, wear-resistant surface. This method is particularly effective for hardening cylinder barrels. By exposing the steel to nitrogen gas at elevated temperatures, a diffusion layer is formed that enhances the material's hardness and fatigue strength without significantly changing the dimensions of the part.

This process is advantageous in that it can improve the wear characteristics of the cylinder barrels, which is critical in maintaining engine performance and longevity. Additionally, nitriding typically occurs at lower temperatures than many other hardening processes, reducing the risk of thermal distortion and preserving the dimensional integrity of the barrels.

In contrast, the other methods listed serve different purposes. Shot peening is used primarily to improve fatigue resistance by introducing compressive stresses on the surface rather than hardening it. Tempering is a heat treatment designed to adjust the hardness and brittleness of steel after it has been hardened, and carburizing involves introducing carbon into the surface of steel, which is more suited for different applications where a softer core and hard outer surface are desired.