Pitting and wear often appear on heavy-duty-axle gears due to their harsh working conditions, such as high torques, high loads, and poor lubrication. Shot peening is a popular surface strengthening method for gears. In order to ensure complete coverage during shot peening, 100~200% coverage is usually prescribed for most gears. However, it is difficult to effectively improve the contact fatigue and wear resistance of heavy-duty-axle gears. Generally, increasing shot peening coverage can heighten the compressive residual stress for prolonging the service lifetime of gears, whereas high coverage levels may cause the deterioration of surface roughness, thus increasing the noise and vibration of gears. To address this issue, this paper deals with the determination of optimal coverage for heavy-duty-axle gears by experimental tests. The influence of shot peening coverage on the surface integrity of gears is analyzed in terms of residual stress, microhardness, surface morphology, and microstructure. The results show that the maximum compressive residual stress increases first and then keeps stable with the increase of coverage, and the maximum value is − 1172.10 MPa. The microhardness peak increases obviously in the beginning and then slowly rises with the increase of coverage, and the maximum value is 747.5 HV_1.0. The surface roughness (Ra) decreases initially and then enhances with the increase of coverage, and the minimum value is 0.99 μm under the coverage of 1000%. The crystallite size can be refined from 36.88 to 28.79 nm by shot peening. The dislocation density increases with the increase of coverage, and the maximum value is 3.70 × 10¹⁶ m⁻². Numerous damages (microscalings, spallings) occur on the treated gear tooth flank affecting the residual stress distribution and roughness under high coverage levels. Meanwhile, the wear behavior of gear steels is investigated, and the wear test results show that shot peening with the coverage of 1000% can lead to a better wear resistance. Taking into consideration of surface integrity and wear test results, the coverage of 1000% is the optimal coverage for heavy-duty-axle gears in shot peening.

重载轴齿轮由于其高扭矩、高负载、润滑不良等恶劣的工作条件，经常出现点蚀和磨损。喷丸强化是一种流行的齿轮表面强化方法。为确保喷丸强化过程中​​的完全覆盖，大多数齿轮通常规定为 100~200% 的覆盖率。然而，很难有效提高重载轴齿轮的接触疲劳和耐磨性。一般来说，增加喷丸覆盖率可以提高压缩残余应力，延长齿轮的使用寿命，而高覆盖率可能会导致表面粗糙度变差，从而增加齿轮的噪音和振动。为了解决这个问题，本文涉及通过实验测试确定重型轴齿轮的最佳覆盖范围。从残余应力、显微硬度、表面形貌和微观结构方面分析喷丸处理对齿轮表面完整性的影响。结果表明，随着覆盖率的增加，最大残余压应力先增加后保持稳定，最大值为-1172.10 MPa。显微硬度峰值开始明显增加，然后随着覆盖度的增加缓慢上升，最大值为747.5 HV_1.0。表面粗糙度（Ra）随着覆盖率的增加先降低后增加，在1000%覆盖率下的最小值为0.99 μm。微晶尺寸可以通过喷丸处理从 36.88 到 28.79 nm 细化。位错密度随着覆盖度的增加而增加，最大值为3.70 × 10 ¹⁶ m ^-2. 处理过的齿轮齿面会出现许多损坏（微鳞、剥落），影响高覆盖水平下的残余应力分布和粗糙度。同时，对齿轮钢的磨损行为进行了研究，磨损试验结果表明，1000%覆盖率的喷丸处理可以产生更好的耐磨性。考虑到表面完整性和磨损测试结果，1000%的覆盖率是重型轴齿轮喷丸处理的最佳覆盖率。