Comparative evaluation of dry, wet, and minimum quantity lubrication (MQL) cooling strategies in the machining of GTD-450 martensitic stainless steel

Machining of high-strength materials, particularly precipitation-hardening martensitic stainless steels, poses a significant challenge, often characterized by high tool wear rates and inferior surface finishes. A review of the literature reveals a lack of information on the optimal machining of GTD-450 steel, particularly regarding the investigation of various lubrication strategies and fluids. To address the identified knowledge gap, this paper presents a comparative analysis of face milling of GTD-450 steel using three cooling modes: dry, wet, and Minimum Quantity Lubrication (MQL). The effects of lubrication strategies and cutting parameters on the machinability attributes, including tool wear (VB) and surface roughness (Ra), were studied. The results denote that MQL offers a better performance and sustainability than other strategies. Specifically, the MQL method achieved a 21.63% reduction in tool wear and a 25.33% improvement in surface finish compared to dry machining. Additionally, wet cooling had notable advantages, resulting in a 12.67% reduction in tool wear and a 15.52% improvement in surface finish. The statistical robustness of our models was validated using Analysis of Variance (ANOVA), which yielded high R-squared values (above 98.9% for tool wear and 98.7% for surface roughness). Statistical modeling, conducted using Minitab software, revealed that the choice of cooling mode had a significant influence on the variations in tool wear. At the same time, the feed rate was the most important variable affecting surface roughness. The optimum process parameters under each lubrication mode were also discovered. The results are currently applied in local turbo-compressor manufacturing sectors.