# A Predictive Model and Comparative Analysis of Laser-Induced Phase Transition Thresholds for Four Key Engineering Alloys

## TL;DR

This paper develops a predictive model to determine laser power thresholds for melting and evaporation in four engineering alloys, enabling precise laser manufacturing.

## Contribution

The study introduces a unified framework and practical tool for comparing laser-material interactions under standardized conditions.

## Key findings

- C26000 brass has the highest melting and evaporation thresholds due to high thermal conductivity.
- Titanium shows the lowest thresholds because of strong heat confinement.
- 42CrMo4 has higher evaporation resistance than SS304 despite similar melting thresholds.

## Abstract

Laser-based manufacturing processes—including marking, hardening, cutting, and welding—demand the precise selection of processing parameters, as the resulting surface state is critically dependent on the delivered power density and beam–material interaction time. This study presents a unified predictive framework for estimating the critical surface power density thresholds for melting qscm and evaporation qscv as functions of scanning speed v for the following four technologically important metallic materials: titanium, C26000 brass, SS304 stainless steel, and 42CrMo4 alloy steel. The principal novelty of this work is twofold. First, it provides the first directly comparative analysis of these four materials under identical, standardized laser conditions (λ = 1064 nm, d = 40 μm, constant absorptivity A = 0.4), eliminating the confounding effects of variable beam geometries and optical assumptions that hinder cross-study comparisons. Second, it translates fundamental thermophysical principles into a practical engineering tool, such as a validated spreadsheet calculator that outputs material-specific threshold curves in real time, enabling rapid, physics-based parameter estimation without recourse to complex numerical simulations. The computed threshold curves exhibit a consistent non-linear increase with scanning speed for all materials, governed by the inverse relationship between interaction time and required power density. The following clear material hierarchy emerges: C26000 brass exhibits the highest thresholds (e.g., qscm = 0.94 × 1010 W/m2, qscv = 10.74 × 1010 W/m2 at v = 100 mm/s) due to its high thermal conductivity, while titanium shows the lowest (qscm = 0.19 × 1010 W/m2, qscv = 0.48 × 1010 W/m2 at v = 100 mm/s) as a consequence of strong heat confinement. SS304 and 42CrMo4 occupy intermediate positions, with 42CrMo4 demonstrating notably higher evaporation resistance than SS304 despite similar melting thresholds. The resulting dual-threshold framework delineates three distinct process regimes—sub-melting heating, melting-dominant processing, and evaporation—providing a quantitative basis for parameter selection in applications ranging from surface hardening to micromachining. By bridging the gap between theoretical material science and applied manufacturing, this work offers a robust, first-order reference for process design and establishes a methodological template for future comparative studies of laser–material interactions.