热处理工艺对激光3D打印成型CX不锈钢组织与性能的影响

Effect of Heat Treatment Process on Microstructure and Properties of 3D Printed CX Stainless Steel

摘要:

为了探究热处理温度对激光选区熔化（Selective laser melting，SLM）技术制备的CX不锈钢微观组织和性能的影响，在不同温度（430、480和530 ℃）下对激光3D打印CX不锈钢进行热处理，并采用XRF、XRD、SEM等方法对样品进行化学成分、组织及性能的分析。结果表明：在SLM打印过程中，导致粉末中Al元素烧损率达19.2%；热处理工艺不影响激光3D打印成型不锈钢的密度，热处理前后样品密度均为7.72 g?cm^-3、致密度达到99%；随着热处理温度升高，CX不锈钢的屈服强度和抗拉强度均有提高，当热处理工艺为480 ℃×10 h（炉冷）时，屈服强度为796.5 MPa、拉伸强度为1 301.5 MPa、硬度为45.2 HRC，相比较打印态，分别提高了60.3%、19.0%和21.4%；断裂伸长率则先提高后降低，经480 ℃×10 h（炉冷）处理后断裂伸长率为16.0%，相较于打印态，提高了12.9%。SEM结果显示，断口为解理断裂和韧窝形貌，属于脆性-韧性混合断裂模式。微观组织分析结果表明：热处理后试样显微组织中的细小树突结构逐渐消失，转而变为粗大的马氏体组织，并且伴随着少量奥氏体的出现；随着热处理温度升高，马氏体转变为边界清晰且粗大的板条状。经热处理后可获得致密度良好、综合力学性能优异的CX不锈钢，为CX不锈钢能运用到更多的应用场景中提供了参考。

Abstract:

This study investigates the impact of heat treatment temperature on the microstructure and properties of CX stainless steel fabricated by selective laser melting （SLM）. Three heat treatment temperatures （430 ℃， 480 ℃， 530 ℃） were applied to the laser 3D printed CX stainless steel， and the samples were analyzed using XRF， XRD， SEM and other techniques to determine their chemical composition， microstructure and properties. The results indicate that the burning loss rate of Al element in the powder during the SLM process is 19.2% . The heat treatment process does not affect the density of the stainless steel produced by laser 3D printing. The samples have a density of 7.72 g?cm^-3 before and after heat treatment with a density of 99%. The yield strength and tensile strength of CX stainless steel increase with increasing heat treatment temperature. The yield strength and tensile strength of CX stainless steel increase with increasing heat treatment temperature. The yield strength and tensile strength are highest when the heat treatment process is carried out at 480 ℃ for 10 h （furnace cooling）， with values of 796.5 MPa and 1 301.5 MPa， respectively. The hardness is 45.2 HRC， which is 60.3%， 19.0%， and 21.4% higher than that of the printed state， respectively. The elongation at break initially increases and then decreases with increasing heat treatment temperature. After heat treatment at 480 ℃×10 h （furnace cooling）， the elongation at break is 16.0%， which is 12.9% higher than that of the printed state. SEM analysis shows that the fracture surface exhibits a brittle-ductile mixed fracture mode with cleavage fracture and dimple morphology. XRD， SEM and metallographic microscope were employed to analyze the microstructure. The fine dendritic structure in the microstructure gradually disappears and is replaced by coarse martensite， accompanied by a small amount of austenite after heat treatment. As the heat treatment temperature increases， the martensite transforms into a lath with clear boundary and large size. The CX stainless steel produced in this experiment has good density and excellent comprehensive mechanical properties， which provides reference for more application scenarios.